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Firebase Crash Course

Css Tricks - Tue, 03/09/2021 - 6:06am

This article is going to help you, dear front-end developer, understand all that is Firebase. We’re going to cover lots of details about what Firebase is, why it can be useful to you, and show examples of how. But first, I think you’ll enjoy a little story about how Firebase came to be.

Eight years ago, Andrew Lee and James Tamplin were building a real-time chat startup called Envolve. The service was a hit. It was used on sites of celebrities like Ricky Martin and Limp Bizkit. Envolve was for developers who didn’t want to—yet again—build their own chat widget. The value of the service came from the setup ease and speed of message delivery. Envolve was just a chat widget. The process was simple. Place a script tag on a page. Once the widget booted up, it would do everything for you. It was like having a database and server for chat messages already set up.

James and Andrew noticed a peculiar trend as the service became more popular. Some developers would include the widget on the page, but make it invisible. Why would someone want a chat widget with hidden messages? Well, it wasn’t just chat data being sent between devices. It was game data, high scores, app settings, to-dos, or whatever the developer needed to quickly send and synchronize. Developers would listen for new messages in the widget and use them to synchronize state in their apps. This was an easy way to create real-time experiences without the need for a back end.

This was a light bulb moment for the co-founders of Firebase. What if developers could do more than send chat messages? What if they had a service to quickly develop and scale their applications? Remove the responsibility of managing back-end infrastructure. Focus on the front end. This is how Firebase was born.

What is Firebase?

Isn’t Firebase a database? No… yes… mostly no. Firebase is a platform that provides the infrastructure for developers and tools for marketers. But it wasn’t always that way.

Seven years ago, Firebase was a single product: a real-time cloud database. Today, Firebase is a collection of 19 products. Each product is designed to empower a part of an application’s infrastructure. Firebase also gives you insight into how your app is performing, what your users are doing, and how you can make your overall app experience better. While Firebase can make up the entirety of your app’s back-end, you can use each product individually as well.

Here’s just a sampling of those 19 products:

  • Hosting: Deploy a new version of your site for every GitHub pull request.
  • Firestore: Build apps that work in real time, even while offline, with no server required.
  • Auth: Authenticate and manage users with a myriad of providers.
  • Storage: Manage user-generated content like photos, videos, and GIFs.
  • Cloud Functions: Server code driven by events (e.g. record created, user sign up, etc.).
  • Extensions: Pre-packaged functions set up with UI (e.g. Stripe payments, text translations, etc.)
  • Google Analytics: Understand user activity, organized by segments and audiences.
  • Remote Config: Key-value store with dynamic conditions that’s great for feature gating.
  • Performance Monitoring: Page load metrics and custom traces from real usage.
  • Cloud Messaging: Cross-platform push notifications.

Whew. That’s a lot, and I didn’t even list the other nine products. That’s okay. There’s no requirement to use every specific service or even more than one thing. But now it’s time to make these services a little more tangible and showcase what you can do with Firebase.

A great way to learn is by seeing something just work. The first section below will get you set up with Firebase services. The sections following that will highlight the Firebase details of a demo app to showcase how to use Firebase features. While this is a relatively thorough guide to Firebase, it’s not a step-by-step tutorial. The goal is to highlight the working bits in the embedded demos for the sake of covering more ground in this one article. If you want step-by-step Firebase tutorials, leave a comment to hype me up to write one.

A basic Firebase setup

This section is helpful if you plan on forking the demo with your own Firebase back end. You can skip this section if you’re familiar with Firebase Projects or just want to see the shiny demos.

Firebase is a cloud-based service which means you need to do some basic account setup before using its services. Firebase development is not tied to a network connection, however. It’s very much worth noting that you can (and usually should) run Firebase locally on your machine for development. This guide demonstrates building an app with CodePen, which means it needs a cloud-connected service. The goal here is to create your personal back end with Firebase and then retrieve the configuration the front end needs to connect to it.

Create a Firebase Project

Go to the Firebase Console. You’ll be asked if you want to set up Google Analytics. None of these examples use it, so you can skip it and always add it back in later if needed.

Create a web Firebase App

Next, you’ll see options for creating an “App.” Click the web option and give it a name—any name will do. Firebase Projects can hold multiple “apps.” I’m not going to get deep into this hierarchy because it’s not too important when getting started. Once the app is created you’ll be given a configuration object.

let firebaseConfig = { apiKey: "your-key", authDomain: "your-domain.firebaseapp.com", projectId: "your-projectId", storageBucket: "your-projectId.appspot.com", messagingSenderId: "your-senderId", appId: "your-appId", measurementId: "your-measurementId" };

This is the configuration you’ll use on the front end to connect to Firebase. Don’t worry about any of these properties in terms of security. There’s nothing insecure about including these properties in your front-end code. You’ll learn in one of the sections below how security works in Firebase.

Now it’s time to represent this “App” you created in code. This “app” is merely a container that shares logic and authentication state across different Firebase services. Firebase provides a set of libraries that make development a lot easier. In this example I’ll be using them from a CDN, but they also work well with module bundlers like Webpack and Rollup.

// This pen adds Firebase via the "Add External Scripts" option in codepen // https://www.gstatic.com/firebasejs/8.2.10/firebase-app.js // https://www.gstatic.com/firebasejs/8.2.10/firebase-auth.js // Create a Project at the Firebase Console // (console.firebase.google.com) let firebaseConfig = { apiKey: "your-key", authDomain: "your-domain.firebaseapp.com", projectId: "your-projectId", storageBucket: "your-projectId.appspot.com", messagingSenderId: "your-senderId", appId: "your-appId", measurementId: "your-measurementId" }; // Create your Firebase app let firebaseApp = firebase.initializeApp(firebaseConfig); // The auth instance console.log(firebaseApp.auth());

Great! You are so, so close to being able to talk to your very own Firebase back end. Now you need to enable the services you intend to use.

Enable authentication providers

The examples below use authentication to sign in users and secure data in the database. When you create a new Firebase Project, all of your authentication providers are turned off. This is initially inconvenient, but essential for security. You don’t want users trying to sign in with providers your back end does not support.

To turn on a provider go to the Authentication tab in the side navigation and then click the “Sign-in method” button up top. Below, you’ll see a large list of providers such as Email and Password, Google, Facebook, GitHub, Microsoft, and Twitter. For the examples below, you will need to turn on Google and Anonymous. Google is near the top of the list and Anonymous is at the bottom. Selecting Google will ask you to provide a support email, I recommend putting in your own personal email while testing, but production apps should have a dedicated email.

If you plan on using authentication within CodePen, then you’ll also need to add CodePen as an authorized domain. You can add authorized domains towards the bottom of the “Sign-in method” tab.

An important note on this authorization: this will allow any project hosted on cdpn.io to sign into your Firebase Project. There’s not a lot of risk for short-term demo purposes. There’s no cost to using Firebase Auth except for phone number authentication. Ideally, you would not want to keep this as an authorized domain if you plan on using this app in a production capacity.

Now, on to the last step in the Firebase Console: Creating a Firestore database!

Create a Firestore database

Click on Firestore in the left navigation. From here, you’ll need to click the button to create the Firestore database. You’ll be asked if you want to start in “production mode” or “test mode.” You want “test mode” for this example. If you’re worried about security, we’ll cover that in the last section.

Now that you have the basics down, let’s get to some real-life use cases.

Authenticating users

The best parts of an app are usually behind a sign-up form. Why don’t we just let the user in as a guest so they can see for themselves? Systems often require accounts because the back end isn’t designed for guests. There’s a system requirement to have a sacred userId property to save any record belonging to a user. This is where “guest” accounts are helpful. They provide low friction for users to join while giving them a temporary userId that appeases the system. Firebase Auth has a process for doing just this.

Setting up anonymous auth

One of my favorite features about Firebase Auth is anonymous auth. There are two perks. One, you can authenticate a user without taking any input (e.g. passwords, phone number, etc.). Two, you get really good at spelling anonymous. It’s really a win-win situation.

Take this CodePen for example.

CodePen Embed Fallback

It’s a form that lets the user decide if they want to sign in with Google or as a guest. Most of the code in this example is specific to the user interface. The Firebase bits are actually pretty easy.

// Firebase-specific code let firebaseConfig = { /* config */ }; let firebaseApp = firebase.initializeApp(firebaseConfig); // End Firebase-specific code let socialForm = document.querySelector('form.sign-in-social'); let guestForm = document.querySelector('form.sign-in-guest'); guestForm.addEventListener('submit', async submitEvent => { submitEvent.preventDefault(); let formData = new FormData(guestForm); let displayName = formData.get('name'); let photoURL = await getRandomPhotoURL(); // Firebase-specific code let { user } = await firebaseApp.auth().signInAnonymously(); await user.updateProfile({ displayName, photoURL }); // End Firebase-specific code });

In the 17 lines of code above (sans comments), only five of them are Firebase-specific. Four lines are needed to import and configure. Two lines needed to signInAnonymously() and user.updateProfile(). The first sign-in method makes a call to your Firebase back end and authenticates the user. The call returns a result that contains the needed properties, such as the uid. Even with guest users, you can associate data to a user in your back end with this uid. After the user is signed in, the example calls updateProfile on the user object. Even though this user is a guest, they can still have a display name and a profile photo.

Setting up Google auth

The great news is that this works the same exact way with all other permanent providers, like Email and Password, Google, Facebook, Twitter, GitHub, Microsoft, Phone Number, and so much more. Implementing the Google Sign-in only takes a few lines of code as well.

socialForm.addEventListener('submit', submitEvent => { submitEvent.preventDefault(); // Firebase-specific code let provider = new firebase.auth.GoogleAuthProvider(); firebaseApp.auth().signInWithRedirect(provider); // End Firebase-specific code });

Each social style provider initiates a redirect-based authentication flow. That’s a fancy way of saying that the signInWithRedirect method will go to the sign-in page owned by the provider and then return back to your app with the authenticated user. In this case, the user is redirected to Google’s sign-in page, signs in, and then is returned back to your app.

Monitoring authentication state

How do you get the user back from this redirect? There are a few ways, but I’m going to go with the most common. You can detect the authentication state of any active user whether logged in or out.

firebaseApp.auth().onAuthStateChanged(user => { if(user != null) { console.log(user.toJSON()); } else { console.log("No user!"); } });

The onAuthStateChanged method updates whenever there is a change in a user’s authentication state. It will fire initially on page load telling you if a user is logged in, logs in, or logs out. This allows you to build a UI that reacts to these state changes. It also fits well into client-side routers because it can redirect a user to the proper page with a small amount of code.

The app in this case just uses <template> tags to replace the contents of the “phone” element. If the user is logged in, the app routes to the new template.

<div class="container"> <div class="phone"> <!-- Phone contents replaced with template tags --> </div> </div>

This provides a simple relationship. The .phone is the “root view.” Each <template> tag is a “child view.” The authentication state determines which view is shown.

firebaseApp.auth().onAuthStateChanged(user => { if(user != null) { // Show demo view routeTo("demo", firebaseApp, user); } else { console.log("No user!"); // Show log in page routeTo("signIn", firebaseApp); } });

The embedded demo isn’t “production ready” as the requirements were just work inside a single CodePen. The goal was to make it easy to read with each “view” contained within a template tag. This loosely emulates what a common routing solution would look like with a framework.

One important bit to note here is that the user object is passed down to the routeTo function. Getting the logged-in state is asynchronous. I find that it’s much easier to pass the user state down for the view than to make async calls from within the view. Many framework routers have a spot for this kind of async data fetching.

Convert guests to permanent users

The <template id="demo"> tag has a submit button for converting guests to permanent users. This is done by having the user sign in with the main provider (again, Google in this case).

let convertForm = document.querySelector('form.convert'); convertForm.addEventListener("submit", submitEvent => { submitEvent.preventDefault(); let provider = new firebase.auth.GoogleAuthProvider(); firebaseApp.auth().currentUser.linkWithRedirect(provider); });

Using the linkWithRedirect method will kick the user out to authenticate with the social provider. When the redirect returns the account will be merged. There’s nothing you have to change within the onAuthStateChanged method that controls the “child view” routing. What’s important to note is that the uid remains the same.

Handling account merging errors

A few edge cases can pop-up when you merge accounts. In some cases, a user could already have created an account with Google and is now trying to merge that existing account. There are many ways you can handle this scenario depending on how you want your app to work. I’m not going to get deep into this because we have a lot more to cover, but it’s important to know how to handle these errors.

async function checkForRedirect() { let auth = firebaseApp.auth(); try { let result = await auth.getRedirectResult(); } catch (error) { switch(error.code) { case 'auth/credential-already-in-use': { // You can check for the provider(s) in use let providers = await auth.fetchProvidersForEmail(error.email); // Then decide what strategy to take. A possible strategy is // notifying the user and asking them to sign in as that account } } } }

The code above uses the getRedirectResult method to detect if a user has directly returned from a social login redirect. If so, there’s a lot of information in that result. Most importantly here, we want to know if there was a problem. Firebase Auth will throw an error and provide relevant information on the error, such as the email and credentials, which will allow you to continue to merge the account. That’s not always what you want to do. In this case, I would probably indicate to the user that the account exists and prompt them to sign in with it. But I digress; I could talk sign-in forms for ages.

Now it’s on to building the data visualization (okay, it’s just a pie-chart) and providing it with a realtime data stream.

Setting up the data visualization

I’ll be honest. I have no idea what this app really does. I really wanted to test out building pie charts with a conic-gradient. I was excited about using CSS Custom Properties to change the values of the chart and syncing that in real time with a database, like Firestore. Let’s take a brief little detour to discuss how conic-gradient works.

A conic-gradient is a surprisingly well-supported CSS feature. Its key feature is that its color-stops are placed at the circumference of the circle.

.pie-chart { background-image: conic-gradient( purple 10%, /* 10% of the circumference */ magenta 0 20%, /* start at 0 go 20%, acts like 10% */ cyan 0 /* Fill the rest */ ); } CodePen Embed Fallback

You can build a pie chart with some quick math: lastStopPercent + percent. I stored these values in four CSS Custom Properties in the app pen: --pie-{n}-value (replace n with a number). Those values are used in another custom property that serves like a computed function.

:root { --pie-1-value: 10%; --pie-2-value: 10%; --pie-3-value: 80%; --pie-1-computed: var(--pie-1-value); --pie-2-computed: 0 calc(var(--pie-1-value) + var(--pie-2-value)); --pie-3-computed: 0 calc(var(--pie-2-value) + var(--pie-3-value)); }

Then the computed values are set in the conic-gradient.

background-image: conic-gradient( purple var(--pie-1-computed), magenta var(--pie-2-computed), cyan 0 );

The last computed value, --pie-3-computed, is ignored since it will always fill to the end (kinda like z for SVG paths). I think it’s still a good idea to set it in JavaScript to make the whole thing feel like it makes sense.

function setPieChartValue(percentage, index) { let root = document.documentElement; root.style.setProperty(`--pie-${index+1}-value`, `${percentage}%`); } let percentages = [25, 35, 60]; percentages.forEach(setPieChartValue);

You can hook up with pie chart with any data set with this newfound knowledge. The Firestore database has a .onSnapshot() method that streams data back from your database.

const fullPathDoc = firebaseApp.firestore().doc('/users/1234/expenses/3-2021'); fullPathDoc.onSnapshot(snap => { const { items } = doc.data(); items.forEach(setPieChartValue); });

A real time update will trigger the .onSnapshot() method whenever a value changes in your Firestore database at that document location. Now you might be asking yourself, what is a document location? How do I even store data in this database in the first place? Let’s take a dive into how Firestore works and how to model data in NoSQL databases.

How to model data in NoSQL database

Firestore is a document (NoSQL) database. It provides a hierarchical pattern of collections, which is a list of documents. Think of a document like a JSON object that has many more data types. A document can have a collection itself, which is known as a sub-collection. This is good for structuring data in a “parent-child” or hierarchical pattern.

If you haven’t followed the pre-requisites section up top, give it a read to make sure you have a Firestore database created before using any of this code yourself.

Just like Auth, you first need to import Firestore up top.

// This pen adds Firebase via the "Add External Scripts" option in codepen // https://www.gstatic.com/firebasejs/8.2.10/firebase-app.js // https://www.gstatic.com/firebasejs/8.2.10/firebase-auth.js // https://www.gstatic.com/firebasejs/8.2.10/firebase-firestore.js let firebaseConfig = { /* config */ }; let firebaseApp = firebase.initializeApp(firebaseConfig);

This tells the Firebase client library how to connect your Firestore database. Using this setup, you can create a reference to a piece of data in your database.

// Reference to collection stored at: '/expenses' const expensesCol = firebaseApp.firestore('expenses'); // Retrieve a snapshot of data (not in realtime) // Top level await is coming! (v8.dev/features/top-level-await) const snapshot = await expensesCol.get(); const expenses = snapshot.docs.map(d => d.data());

The code above creates a “Collection Reference” and then calls the .get() method to retrieve the data snapshot. This is not the data itself; it’s a wrapper that has a lot of helpful methods and metadata about the data. The last line “unwraps” the snapshot by iterating over the .docs array and calling the .data() function for each “Document Snapshot.” Note that this isn’t real time, but that’s coming up in just a bit!

What’s really important to grok here is the data structure (sometimes called a data model). This app stores the “expenses” of a user. Let’s say the document has the following structure.

{ uid: '1234', items: [ { label: "Food", value: 10 }, { label: "Services", value: 24 }, { label: "Rent", value: 30 }, { label: "Oops", value: 38 } ] }

The properties of a document are called a field. This document has an array field of items. Each item contains a label string and a value number. There’s also a string field named uid that stores the id of the user who owns the data. This structure simplifies the process of iterating over the values to create the pie chart. That part is solved, but how do we figure out how to get to a specific user’s expenses?

A traditional way of retrieving data based on a constraint is by using a query. That’s something you can do in Firestore with a .where() method.

// Let's pretend currentUser.uid === '1234' const currentUser = firebaseApp.auth().currentUser; // Reference to collection stored at: '/expenses' const expensesCol = firebaseApp.firestore('expenses'); // Query for the expenses belonging to uid == 1234 const userQuery = expensesCol.where('uid', '==', currentUser.uid); const snapshot = await userQuery.get();

This structure is fine but doesn’t take full advantage of the hierarchy provided by collections and, more importantly, sub-collections. Instead, you can structure your data in a “parent-child” relationship. Structures in Firestore work a lot like URLs for a website. You can design the paths to contain route parameter-like wildcards.


The path above structures the data with a top-level collection of /users, then a document assigned to a uid, followed by a sub-collection. Sub-collections can exist even if there’s no existing parent document. Each sub-collection contains a document where you can retrieve the expenses by putting in the year as a number (e.g. 3 for March) and the year (2021).

// Let's pretend currentUser.uid === '1234' const currentUser = firebaseApp.auth().currentUser; // Reference to collection stored at: '/users' const usersCol = firebaseApp.firestore().collection('users'); // Reference to document stored at: '/users/1234'; const userDoc = usersCol.doc(currentUser.uid); // Reference to sub-collection stored at: '/users/1234/expenses' const userExpensesCol = userDoc.collection('expenses'); // Reference to document stored at: '/users/1234/expenses/3-2021'; const marchDoc = userExpensesCol.doc('3-2021'); // Alternatively, you could express a full path: const fullPathDoc = firebaseApp.firestore().doc('/users/1234/expenses/3-2021');

The example above shows that, with a little bit of modeling, you can retrieve a piece of data without needing to write a query. This won’t always be the case for each and every data structure. In many cases, it will be valid to have a top-level collection. It comes down to the kind of queries you want to write and how you want to secure your data. It’s good, however, to know your options when modeling the data. If you want to learn more about this topic, my colleague Todd Kerpelman has recorded a comprehensive series all about Firestore.

We’re going to go with the hierarchical approach in this app. With this data structured let’s stream in real time.

Streaming data to the visualization

The section above detail how to retrieve data in a “one-time” manner with .get(). Both documents and collections also have a .onSnapshot() method that allows you to stream the data in realtime.

const fullPathDoc = firebaseApp.firestore().doc('/users/1234/expenses/3-2021'); fullPathDoc.onSnapshot(snap => { const { items } = doc.data(); items.forEach((item, index) => { console.log(item); }); });

Whenever an update happens for the data stored at fullPathDoc, Firestore will stream the update to all connected clients. Using this data sync you can set all the CSS Custom Properties for the pie chart.

let db = firebaseApp.firestore(); let { uid } = firebaseApp.auth().currentUser; let marchDoc = db.doc(`users/${uid}/expenses/3-2021`); marchDoc.onSnapshot(snap => { let { factors } = snap.data(); factors.forEach((factor, index) => { root.style.setProperty(`--pie-${index+1}__value`, `${factor.value}%`); }); });

Now for the fun part! Go update the data in the database and see the pie slices move around.

Honestly, that is so much fun. I’ve been working on Firebase for nearly seven years and I never get tired of seeing the lightning-fast data updates. But the job is not yet complete! The database is insecure as it can be updated by anyone anywhere. It’s time to make sure it’s secure only to the user who owns that data.

Securing your database

If you’re new to Firebase or back-end development, you might be wondering why the database is insecure at the current moment. Firebase allows you to build apps without running your own server. This means you can connect to a database directly from the browser. So, if it’s that easy to access the database, what keeps someone from coming along and doing something malicious? The answer is Firebase Security Rules.

Security Rules are how you secure access to your Firebase services. You write a set of rules that specify how data is accessed in your back end. Firebase evaluates these rules for each request that comes into your back end and only allows the request if it passes the rule. In other words, you write a set of rules and Firebase runs them on the server to secure access to your services.

Security Rules are like a router

Security Rules are a custom language that works a lot like a router.

rules_version = '2'; service cloud.firestore { match /databases/{database}/documents { // When a request comes in for a "user/:userId" // let's allow the read or write (not very secure) // Don't copy this in your code plz! match /users/{userId} { allow read, write: if userId == "david"; } } }

The example above starts with a rules_version statement. Don’t worry too much about that, but it’s how you tell Firebase the version of the Security Rules language you want to use. Currently, it’s recommended to use version 2. Then the example goes on to create a service declaration. This tells Firebase what service you are trying to secure, which is Firestore in this case. Now, on to the important part: the match statements.

A match statement is the part that makes rules work like a router. The first match statement in the example establishes that you are matching for documents in the database. It’s a very general statement that says, Hey, look in the documents section. The next match statement is more specific. It looks to match a document within the users collection. The path syntax of /users/{userId} is similar to a routing syntax of /users/:userId where the :userId syntax notes a route parameter. In Security Rules, the {userId} syntax works just like route parameter, except that it’s called “wildcard” here. Any user within the collection can be matched with this statement. What happens when the user is matched? You use the allow statement to control the access.

The allow statement evaluates an expression and, if the result is true, it allows the operation. If it’s false, the operation is rejected. What’s useful about the allow statement is that there’s a lot of useful information to use in the containing match block. One useful piece of information is the wildcard itself. The example above uses the userId wildcard like a variable and tests to see if it matches the value of "``david``". Only a userId of "``david``" will allow the read or write operation.

Now that’s not a very useful rule, but it helps to start simple. Let’s take a moment to remember the structure of the database. Security Rules are a lot like an annotation on top of your data structure. You can make notes at the document paths that enforce your data access. This app stores data at a /users/{userId} collection and expenses at a /users/{userId}/expenses/month-year sub-collection. The security strategy is to ensure that only the authenticated user can read or write their data.

rules_version = '2'; service cloud.firestore { match /databases/{database}/documents { match /users/{userId}/{documents=**} { allow read, write: if request.auth.uid == userId; } } }

The example above starts off the same but starts to change when matching the /users/{userId} path. There’s this weird {documents=**} syntax tacked on at the end. This is called the recursive wildcard and it’s a way of cascading a rule to sub-collections—meaning any sub-collection of /users/{userId} will have the same rules applied to it. This is great in the current use case because both /users/{userId} and /users/{userId}/expenses/month-year should follow the same rule.

Inside of that match, the allow statement has been updated with a new variable named request. Security Rules come with an entire set of variables to help you write sophisticated rules. This variable is how you evaluate if the request comes from an authenticated user. The allow statement evaluates if the authenticated user has a uid that matches the {userId} wildcard. If that statement evaluates to true, the read or write is allowed. If the user is not authenticated or does not match the {userId} wildcard, no operation is allowed. Therefore, it’s secure!

The following snippet shows two requests from an authenticated user.

// Let's pretend currentUser.uid === '1234' const currentUser = firebaseApp.auth().currentUser; // The authenticated user owns this sub-collection const ownedDoc = firebaseApp.firestore().doc('/users/1234/expenses/3-2021'); // The authenticated user DOES NOT own this sub-collection const notOwnedDoc = firebaseApp.firestore().doc('/users/abcxyz/expenses/3-2021'); try { const ownedSnapshot = await ownedDoc.get(); const notOwnedSnapshot = await notOwnedDoc.get(); } catch (error) { // This will result in an error because the `notOwnedDoc` request will fail the security rule }

Just like that, you have secured a collection and a sub-collection. But what about the rest of the data in the database? What happens if you don’t write any rules for data at those paths? The example above will only allow access that matches the allow statement for the /users collection and its sub-collections. No other reads or writes will work, at all, for any other collections or sub-collections. In other words, if you don’t write an allow statement for a path, then it won’t allow any reads or writes. This is a great default for security because it makes you explicitly enforce your access at the appropriate paths. You can mess this up, however!

rules_version = '2'; service cloud.firestore { match /databases/{database}/documents { // Ahh!!! Never do this in a production app!!! // This will negate any rule you write below!! // Don't copy and paste this into your rules!! match /{document=**} { allow read, write: if true; } match /users/{userId}/{documents=**} { allow read, write: if request.auth.uid == userId; } } }

The sample above adds a match block that matches the path of /{document=**}. This is a recursive wildcard path that matches every document in the entire database. The allow statement always evaluates to true because it is true. This match block creates an overlapping match statement, meaning two or more match blocks that match on the same path. This isn’t like CSS where the last rule wins. Security Rules will evaluate each rule matched and if any of them evaluate to true, the operation is allowed. Therefore, the global recursive wildcard will negate any secure rule you have below. The global recursive wildcard is a strategy for opening up your database for a short-term “test mode” where there is no important non-publicly accessible data (nothing private or important) saved. Outside of that, I don’t recommend using it.

Write rules locally or in the console

The final topic to touch upon is where you write and save your rules. You have two options. The first is inside of the Firebase Console. Within the Firestore data viewer you’ll see an option for “Rules.” This tab shows you the rules that are active for your database. From here, you can write and even test scenarios against your rules. This approach is recommended for those who are getting started and trying to become familiar with Security Rules.

Another option is write rules locally on your machine and use the Firebase CLI to deploy them to the console. This allows you to keep them in source control and write tests for them to make sure they continue to work as your codebase evolves. This is the recommended approach for production apps and teams.

It’s worth noting again that your Firebase configuration used to create a Firebase App is not insecure. It’s the equivalent of someone knowing the domain name of your site. Someone knowing your domain name doesn’t make your site insecure. Security Rules are Firebase’s way of providing secure access to your data and your services.

Wrapping things up

That was a lot of Firebase information, especially about all the stuff about rules (security is important!). The information in this article signs in users, merges guest accounts, structures data, streams it to a visualization in real time, and makes sure it’s all secure. You can use these concepts to build so many different applications.

There are so many things I want you to know if you want to continue building with Firebase, such as the Emulator Suite. The app built in this article can run locally on your machine, which is a far easier development experience and great for testing in CI/CD environments. There are also a lot of great Firebase tools and framework libraries. Here are some links worth checking out.

If there’s one thing I hope you saw in this article, it’s that there aren’t too many lines of front-end Firebase code. A line here to sign in a user, a few lines there to get the data, but mostly code that’s specific to the app itself. The goal of Firebase is to allow you to build quickly. Remove the responsibility of managing backend infrastructure. Focus on the front end.

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AutomateWoo Brings Automated Communications to Bookings

Css Tricks - Tue, 03/09/2021 - 5:00am

AutomateWoo is this handy extension for WooCommerce that adds triggers actions based on your online store’s activity. Someone abandoned their cart? Remind them by email. Someone made a purchase? Ask them to leave a review or follow up to see how they’re liking the product so far.

This sort of automated communication is gold. Automatically reaching out to customers based on their own activity keeps them engaged and encourages more activity, hopefully the kind that makes you more money.

AutomateWoo now integrates with WooCommerce Bookings and it includes a new trigger: booking status changes. So now, when a customer’s appointment changes—say from “pending” to “confirmed”—AutomateWoo can perform an action, like sending an email confirming the customer’s booked appointment. Or asking for feedback after the appointment. Or reminding a customer to book a follow-up appointment.

Or really anything else you can think of based on the status of a booking. It’s like having your own version of Zapier right in WordPress, but without having to manage another platform.

Once a customer’s booking status for a river rafting adventure is confirmed, they’ll get an email not only confirming the appointment but with any additional information they might need to know. OK, real-life situation.

Sometime in the middle of last year, I was working with a client that takes online appointments, or bookings. The user finds an open spot on a calendar and books that time to come in for service. A lot like making a hair appointment.

Well, what happens when a bunch of appointments need to be canceled? I don’t need to tell you what a big deal that was this time last year. This particular client had the unfortunate task of reaching out to each and every customer and updating the status of over 200 appointments.

That was awful. Fortunately, we found a way to bulk update the appointments. Then we sent a mass email to everyone with a canceled appointment. Not the most elegant solution, but it got the job done. I’ll tell you what, though, it would have been a heckuva lot less work and the communications would have been much polished if we had this AutomateWoo + WooCommerce Bookings combo. Simply create a trigger for a canceled status change, write the email, and bulk update the bookings statuses.

AutomateWoo and WooCommerce Bookings are both paid extensions for WooCommerce. The licenses will run you $349, which includes a year of updates and customer support. The value you get out of it really depends on your overall budget and how much activity happens on your site. I can tell you that would’ve been a stellar deal when we were trying to resolve 200+ canceled appointments. And if it leads to additional bookings, upsells, and fewer cancelations (because, hey, research has shown that 75% of email revenue is generated by triggered campaigns), then it could very well pay for itself.

You can give WooCommerce Bookings a front-end test drive with a live demo. Both extensions also come with a 30-day money-back guarantee, giving you a good amount of time to try them out.

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Web Components Are Easier Than You Think

Css Tricks - Mon, 03/08/2021 - 6:06am

When I’d go to a conference (when we were able to do such things) and see someone do a presentation on web components, I always thought it was pretty nifty (yes, apparently, I’m from 1950), but it always seemed complicated and excessive. A thousand lines of JavaScript to save four lines of HTML. The speaker would inevitably either gloss over the oodles of JavaScript to get it working or they’d go into excruciating detail and my eyes would glaze over as I thought about whether my per diem covered snacks.

But in a recent reference project to make learning HTML easier (by adding zombies and silly jokes, of course), the completist in me decided I had to cover every HTML element in the spec. Beyond those conference presentations, this was my first introduction to the <slot> and <template> elements. But as I tried to write something accurate and engaging, I was forced to delve a bit deeper.

And I’ve learned something in the process: web components are a lot easier than I remember.

Either web components have come a long way since the last time I caught myself daydreaming about snacks at a conference, or I let my initial fear of them get in the way of truly knowing them — probably both.

I’m here to tell you that you—yes, you—can create a web component. Let’s leave our distractions, fears, and even our snacks at the door for a moment and do this together.

Let’s start with the <template>

A <template> is an HTML element that allows us to create, well, a template—the HTML structure for the web component. A template doesn’t have to be a huge chunk of code. It can be as simple as:

<template> <p>The Zombies are coming!</p> </template>

The <template> element is important because it holds things together. It’s like the foundation of building; it’s the base from which everything else is built. Let’s use this small bit of HTML as the template for an <apocalyptic-warning> web component—you know, as a warning when the zombie apocalypse is upon us.

Then there’s the <slot>

<slot> is merely another HTML element just like <template>. But in this case, <slot> customizes what the <template> renders on the page.

<template> <p>The <slot>Zombies</slot> are coming!</p> </template>

Here, we’ve slotted (is that even a word?) the word “Zombies” in the templated markup. If we don’t do anything with the slot, it defaults to the content between the tags. That would be “Zombies” in this example.

Using <slot> is a lot like having a placeholder. We can use the placeholder as is, or define something else to go in there instead. We do that with the name attribute.

<template> <p>The <slot name="whats-coming">Zombies</slot> are coming!</p> </template>

The name attribute tells the web component which content goes where in the template. Right now, we’ve got a slot called whats-coming. We’re assuming zombies are coming first in the apocalypse, but the <slot> gives us some flexibility to slot something else in, like if it ends up being a robot, werewolf, or even a web component apocalypse.

Using the component

We’re technically done “writing” the component and can drop it in anywhere we want to use it.

<apocalyptic-warning> <span slot="whats-coming">Halitosis Laden Undead Minions</span> </apocalyptic-warning> <template> <p>The <slot name="whats-coming">Zombies</slot> are coming!</p> </template>

See what we did there? We put the <apocalyptic-warning> component on the page just like any other <div> or whatever. But we also dropped a <span> in there that references the name attribute of our <slot>. And what’s between that <span> is what we want to swap in for “Zombies” when the component renders.

Here’s a little gotcha worth calling out: custom element names must have a hyphen in them. It’s just one of those things you’ve gotta know going into things. The spec prescribes that to prevent conflicts in the event that HTML releases a new element with the same name.

Still with me so far? Not too scary, right? Well, minus the zombies. We still have a little work to do to make the <slot> swap possible, and that’s where we start to get into JavaScript.

Registering the component

As I said, you do need some JavaScript to make this all work, but it’s not the super complex, thousand-lined, in-depth code I always thought. Hopefully I can convince you as well.

You need a constructor function that registers the custom element. Otherwise, our component is like the undead: it’s there but not fully alive.

Here’s the constructor we’ll use:

// Defines the custom element with our appropriate name, <apocalyptic-warning> customElements.define("apocalyptic-warning", // Ensures that we have all the default properties and methods of a built in HTML element class extends HTMLElement { // Called anytime a new custom element is created constructor() { // Calls the parent constructor, i.e. the constructor for `HTMLElement`, so that everything is set up exactly as we would for creating a built in HTML element super(); // Grabs the <template> and stores it in `warning` let warning = document.getElementById("warningtemplate"); // Stores the contents of the template in `mywarning` let mywarning = warning.content; const shadowRoot = this.attachShadow({mode: "open"}).appendChild(mywarning.cloneNode(true)); } });

I left detailed comments in there that explain things line by line. Except the last line:

const shadowRoot = this.attachShadow({mode: "open"}).appendChild(mywarning.cloneNode(true));

We’re doing a lot in here. First, we’re taking our custom element (this) and creating a clandestine operative—I mean, shadow DOM. mode: open simply means that JavaScript from outside the :root can access and manipulate the elements within the shadow DOM, sort of like setting up back door access to the component.

From there, the shadow DOM has been created and we append a node to it. That node will be a deep copy of the template, including all elements and text of the template. With the template attached to the shadow DOM of the custom element, the <slot> and slot attribute take over for matching up content with where it should go.

Check this out. Now we can plop two instances of the same component, rendering different content simply by changing one element.

CodePen Embed Fallback Styling the component

You may have noticed styling in that demo. As you might expect, we absolutely have the ability to style our component with CSS. In fact, we can include a <style> element right in the <template>.

<template id="warningtemplate"> <style> p { background-color: pink; padding: 0.5em; border: 1px solid red; } </style> <p>The <slot name="whats-coming">Zombies</slot> are coming!</p> </template>

This way, the styles are scoped directly to the component and nothing leaks out to other elements on the same page, thanks to the shadow DOM.

Now in my head, I assumed that a custom element was taking a copy of the template, inserting the content you’ve added, and then injecting that into the page using the shadow DOM. While that’s what it looks like on the front end, that’s not how it actually works in the DOM. The content in a custom element stays where it is and the shadow DOM is sort of laid on top like an overlay.

And since the content is technically outside the template, any descendant selectors or classes we use in the template’s <style> element will have no affect on the slotted content. This doesn’t allow full encapsulation the way I had hoped or expected. But since a custom element is an element, we can use it as an element selector in any ol’ CSS file, including the main stylesheet used on a page. And although the inserted material isn’t technically in the template, it is in the custom element and descendant selectors from the CSS will work.

apocalyptic-warning span { color: blue; } CodePen Embed Fallback

But beware! Styles in the main CSS file cannot access elements in the <template> or shadow DOM.

Let’s put all of this together

Let’s look at an example, say a profile for a zombie dating service, like one you might need after the apocalypse. In order to style both the default content and any inserted content, we need both a <style> element in the <template> and styling in a CSS file.

The JavaScript code is exactly the same except now we’re working with a different component name, <zombie-profile>.

customElements.define("zombie-profile", class extends HTMLElement { constructor() { super(); let profile = document.getElementById("zprofiletemplate"); let myprofile = profile.content; const shadowRoot = this.attachShadow({mode: "open"}).appendChild(myprofile.cloneNode(true)); } } );

Here’s the HTML template, including the encapsulated CSS:

<template id="zprofiletemplate"> <style> img { width: 100%; max-width: 300px; height: auto; margin: 0 1em 0 0; } h2 { font-size: 3em; margin: 0 0 0.25em 0; line-height: 0.8; } h3 { margin: 0.5em 0 0 0; font-weight: normal; } .age, .infection-date { display: block; } span { line-height: 1.4; } .label { color: #555; } li, ul { display: inline; padding: 0; } li::after { content: ', '; } li:last-child::after { content: ''; } li:last-child::before { content: ' and '; } </style> <div class="profilepic"> <slot name="profile-image"><img src="https://assets.codepen.io/1804713/default.png" alt=""></slot> </div> <div class="info"> <h2><slot name="zombie-name" part="zname">Zombie Bob</slot></h2> <span class="age"><span class="label">Age:</span> <slot name="z-age">37</slot></span> <span class="infection-date"><span class="label">Infection Date:</span> <slot name="idate">September 12, 2025</slot></span> <div class="interests"> <span class="label">Interests: </span> <slot name="z-interests"> <ul> <li>Long Walks on Beach</li> <li>brains</li> <li>defeating humanity</li> </ul> </slot> </div> <span class="z-statement"><span class="label">Apocalyptic Statement: </span> <slot name="statement">Moooooooan!</slot></span> </div> </template>

Here’s the CSS for our <zombie-profile> element and its descendants from our main CSS file. Notice the duplication in there to ensure both the replaced elements and elements from the template are styled the same.

zombie-profile { width: calc(50% - 1em); border: 1px solid red; padding: 1em; margin-bottom: 2em; display: grid; grid-template-columns: 2fr 4fr; column-gap: 20px; } zombie-profile img { width: 100%; max-width: 300px; height: auto; margin: 0 1em 0 0; } zombie-profile li, zombie-profile ul { display: inline; padding: 0; } zombie-profile li::after { content: ', '; } zombie-profile li:last-child::after { content: ''; } zombie-profile li:last-child::before { content: ' and '; }

All together now!

CodePen Embed Fallback

While there are still a few gotchas and other nuances, I hope you feel more empowered to work with the web components now than you were a few minutes ago. Dip your toes in like we have here. Maybe sprinkle a custom component into your work here and there to get a feel for it and where it makes sense.

That’s really it. Now what are you more scared of, web components or the zombie apocalypse? I might have said web components in the not-so-distant past, but now I’m proud to say that zombies are the only thing that worry me (well, that and whether my per diem will cover snacks…)

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Progressive enhancement and accessibility redux

QuirksBlog - Mon, 03/08/2021 - 3:00am

A while ago I asked about the exact relationship between progressive enhancement and accessiblity. What were the responses?

The resulting Twitter thread was interesting, and basically boiled down to this:

Progressive enhancement is an important accessibility tool.

I can agree with that without reservation, but still had a nagging feeling that this was not the entire story.

Then I received a private communication from Josh Fremer that connected the dots for me. His mail is worth quoting at length — with permission:

I think of [progressive enhancement and accessibility] as the same process, but with different foci. Accessibility aims to optimize an experience across a spectrum of user capabilities. Progressive enhancement aims to optimize an experience across a spectrum of user _agent_ capabilities.

Indeed, if you broaden the definition of "user agent" to include a user's physiology, I think the concepts become nearly identical.

What is the application of color to a website if not a progressive enhancement targeting user agents that can discern colors? Whether the "agent" in this case is the electronic device in the user's hands or the cells in their eyes is kind of moot. The principles of both PE and accessibility require us to consider the user who is unable to receive color information.

Conversely, what is the inability to process javascript other than a "disability" of the user agent? We would probably call handling this case a PE concern, but what If the user has disabled javascript in order to mitigate a physical disability? The capabilities of the user agent have been modified to better match the capabilities of the user and now it starts to look like an accessibility issue.

In closing a fun little thought experiment is to imagine a sci fi future in which users can plug computers directly into their brains, or swap their personalities into different bodies with different capabilities. This further blurs the line between what we traditionally call a "user agent" and a user's innate disabilities. "This web site is best viewed in a body with 20/20 vision and quick reflexes."

Food for thought.

(Josh promised to write an article about his idea, which I’ve never seen expressed like this before. If you have seen a similar argument, please let me know. Once Josh’s article is live I’ll include a link in this post.)

CSS-Tricks Chronicle XXXIX

Css Tricks - Fri, 03/05/2021 - 2:05pm

I’ve been lucky enough to be a guest on some podcasts and at some events, so I thought I’d do a quick little round-up here! These Chronicle posts are just that: an opportunity to share some off-site stiff that I’ve been up to. This time, it’s all different podcasts.

Web Rush

Episode 122: Modern Web with Chris Coyier

Chris Coyier talks with John, Ward, Dan, and Craig about the modern web. What technology should we be paying attention to? What tech has Chris used that was worth getting into? Flexbox or CSS Grid? Is there anything better than HTML coming? And what tools should developers be aware of?

Front-end Development South Africa

Live Q&A session with Chris Coyier


Evolving as podcasting grows with Chris Coyier of ShopTalk Show

Craig talks to Chris about what it’s like being an online creator (podcaster, blogger, software and web designer, etc.). Chris talks about the lessons he has learned and what it’s like to have a weekly podcast for ten years. They also talk about podcasting trends in terms of marketing, topics, and the future outlook of the industry.

Cloudinary Devjams

DevJams Episode #2: Fetching Local Production Images With Cloudinary for an Eleventy Site

Watch our hosts Sam Brace and Becky Peltz, as well as our special guest host Eric Portis, interview Chris Coyier about his recent development project. With Eleventy, Netlify, Puppeteer and Cloudinary’s fetch capabilities, he was able to create a microsite for his famous CSS-Tricks.com site that showcases various coding fonts you can use. Find how he did it by watching this episode!

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A Super Flexible CSS Carousel, Enhanced With JavaScript Navigation

Css Tricks - Fri, 03/05/2021 - 5:47am

Not sure about you, but I often wonder how to build a carousel component in such a way that you can easily dump a bunch of items into the component and get a nice working carousel — one that allows you to scroll smoothly, navigate with the dynamic buttons, and is responsive. If that is the thing you’d like to build, follow along and we’ll work on it together!

This is what we’re aiming for:

CodePen Embed Fallback

We’re going to be working with quite a bit of JavaScript, React and the DOM API from here on out.

First, let’s spin up a fresh project

Let’s start by bootstrapping a simple React application with styled-components tossed in for styling:

npx create-react-app react-easy-carousel cd react-easy-carousel yarn add styled-components yarn install yarn start

Styling isn’t really the crux of what we’re doing, so I have prepared aa bunch of predefined components for us to use right out of the box:

// App.styled.js import styled from 'styled-components' export const H1 = styled('h1')` text-align: center; margin: 0; padding-bottom: 10rem; ` export const Relative = styled('div')` position: relative; ` export const Flex = styled('div')` display: flex; ` export const HorizontalCenter = styled(Flex)` justify-content: center; margin-left: auto; margin-right: auto; max-width: 25rem; ` export const Container = styled('div')` height: 100vh; width: 100%; background: #ecf0f1; ` export const Item = styled('div')` color: white; font-size: 2rem; text-transform: capitalize; width: ${({size}) => `${size}rem`}; height: ${({size}) => `${size}rem`}; display: flex; align-items: center; justify-content: center; `

Now let’s go to our App file, remove all unnecessary code, and build a basic structure for our carousel:

// App.js import {Carousel} from './Carousel' function App() { return ( <Container> <H1>Easy Carousel</H1> <HorizontalCenter> <Carousel> {/* Put your items here */} </Carousel> </HorizontalCenter> </Container> ) } export default App

I believe this structure is pretty straightforward. It’s the basic layout that centers the carousel directly in the middle of the page.

Now, let’s make the carousel component

Let’s talk about the structure of our component. We’re gonna need the main <div> container which as our base. Inside that, we’re going to take advantage of native scrolling and put another block that serves as the scrollable area.

// Carousel.js <CarouserContainer> <CarouserContainerInner> {children} </CarouserContainerInner> </CarouserContainer>

You can specify width and height on the inner container, but I’d avoid strict dimensions in favor of some sized component on top of it to keep things flexible.

Scrolling, the CSS way

We want that scroll to be smooth so it’s clear there’s a transition between slides, so we’ll reach for CSS scroll snapping, set the scroll horizontally along the x-axis, and hide the actual scroll bar while we’re at it.

export const CarouserContainerInner = styled(Flex)` overflow-x: scroll; scroll-snap-type: x mandatory; -ms-overflow-style: none; scrollbar-width: none; &::-webkit-scrollbar { display: none; } & > * { scroll-snap-align: center; } `

Wondering what’s up with scroll-snap-type and scroll-snap-align? That’s native CSS that allows us to control the scroll behavior in such a way that an element “snaps” into place during a scroll. So, in this case, we’ve set the snap type in the horizontal (x) direction and told the browser it has to stop at a snap position that is in the center of the element.

In other words: scroll to the next slide and make sure that slide is centered into view. Let’s break that down a bit to see how it fits into the bigger picture.

Our outer <div> is a flexible container that puts it’s children (the carousel slides) in a horizontal row. Those children will easily overflow the width of the container, so we’ve made it so we can scroll horizontally inside the container. That’s where scroll-snap-type comes into play. From Andy Adams in the CSS-Tricks Almanac:

Scroll snapping refers to “locking” the position of the viewport to specific elements on the page as the window (or a scrollable container) is scrolled. Think of it like putting a magnet on top of an element that sticks to the top of the viewport and forces the page to stop scrolling right there.

Couldn’t say it better myself. Play around with it in Andy’s demo on CodePen.

But, we still need another CSS property set on the container’s children (again, the carousel slides) that tells the browser where the scroll should stop. Andy likens this to a magnet, so let’s put that magnet directly on the center of our slides. That way, the scroll “locks” on the center of a slide, allowing to be full in view in the carousel container.

That property? scroll-snap-align.

& > * { scroll-snap-align: center; }

We can already test it out by creating some random array of items:

const colors = [ '#f1c40f', '#f39c12', '#e74c3c', '#16a085', '#2980b9', '#8e44ad', '#2c3e50', '#95a5a6', ] const colorsArray = colors.map((color) => ( <Item size={20} style={{background: color, borderRadius: '20px', opacity: 0.9}} key={color} > {color} </Item> ))

And dumping it right into our carousel:

// App.js <Container> <H1>Easy Carousel</H1> <HorizontalCenter> <Carousel>{colorsArray}</Carousel> </HorizontalCenter> </Container> CodePen Embed Fallback

Let’s also add some spacing to our items so they won’t look too squeezed. You may also notice that we have unnecessary spacing on the left of the first item. We can add a negative margin to offset it.

export const CarouserContainerInner = styled(Flex)` overflow-x: scroll; scroll-snap-type: x mandatory; -ms-overflow-style: none; scrollbar-width: none; margin-left: -1rem; &::-webkit-scrollbar { display: none; } & > * { scroll-snap-align: center; margin-left: 1rem; } `

Take a closer look at the cursor position while scrolling. It’s always centered. That’s the scroll-snap-align property at work!

And that’s it! We’ve made an awesome carousel where we can add any number of items, and it just plain works. Notice, too, that we did all of this in plain CSS, even if it was built as a React app. We didn’t really need React or styled-components to make this work.

CodePen Embed Fallback Bonus: Navigation

We could end the article here and move on, but I want to take this a bit further. What I like about what we have so far is that it’s flexible and does the basic job of scrolling through a set of items.

But you may have noticed a key enhancement in the demo at the start of this article: buttons that navigate through slides. That’s where we’re going to put the CSS down and put our JavaScript hats on to make this work.

First, let’s define buttons on the left and right of the carousel container that, when clicked, scrolls to the previous or next slide, respectively. I’m using simple SVG arrows as components:

// ArrowLeft export const ArrowLeft = ({size = 30, color = '#000000'}) => ( <svg xmlns="http://www.w3.org/2000/svg" width={size} height={size} viewBox="0 0 24 24" fill="none" stroke={color} strokeWidth="2" strokeLinecap="round" strokeLinejoin="round" > <path d="M19 12H6M12 5l-7 7 7 7" /> </svg> ) // ArrowRight export const ArrowRight = ({size = 30, color = '#000000'}) => ( <svg xmlns="http://www.w3.org/2000/svg" width={size} height={size} viewBox="0 0 24 24" fill="none" stroke={color} strokeWidth="2" strokeLinecap="round" strokeLinejoin="round" > <path d="M5 12h13M12 5l7 7-7 7" /> </svg> )

Now let’s position them on both sides of our carousel:

// Carousel.js <LeftCarouselButton> <ArrowLeft /> </LeftCarouselButton> <RightCarouselButton> <ArrowRight /> </RightCarouselButton>

We’ll sprinkle in some styling that adds absolute positioning to the arrows so that the left arrow sits on the left edge of the carousel and the right arrow sits on the right edge. A few other things are thrown in to style the buttons themselves to look like buttons. Also, we’re playing with the carousel container’s :hover state so that the buttons only show when the user’s cursor hovers the container.

// Carousel.styled.js // Position and style the buttons export const CarouselButton = styled('button')` position: absolute; cursor: pointer; top: 50%; z-index: 1; transition: transform 0.1s ease-in-out; background: white; border-radius: 15px; border: none; padding: 0.5rem; ` // Display buttons on hover export const LeftCarouselButton = styled(CarouselButton)` left: 0; transform: translate(-100%, -50%); ${CarouserContainer}:hover & { transform: translate(0%, -50%); } ` // Position the buttons to their respective sides export const RightCarouselButton = styled(CarouselButton)` right: 0; transform: translate(100%, -50%); ${CarouserContainer}:hover & { transform: translate(0%, -50%); } `

This is cool. Now we have buttons, but only when the user interacts with the carousel.

But do we always want to see both buttons? It’d be great if we hide the left arrow when we’re at the first slide, and hide the right arrow when we’re at the last slide. It’s like the user can navigate past those slides, so why set the illusion that they can?

I suggest creating a hook that’s responsible for all the scrolling functionality we need, as we’re gonna have a bunch of it. Plus, it’s just good practice to separate functional concerns from our visual component.

First, we need to get the reference to our component so we can get the position of the slides. Let’s do that with ref:

// Carousel.js const ref = useRef() const position = usePosition(ref) <CarouserContainer> <CarouserContainerInner ref={ref}> {children} </CarouserContainerInner> <LeftCarouselButton> <ArrowLeft /> </LeftCarouselButton> <RightCarouselButton> <ArrowRight /> </RightCarouselButton> </CarouserContainer>

The ref property is on <CarouserContainerInner> as it contains all our items and will allow us to do proper calculations.

Now let’s implement the hook itself. We have two buttons. To make them work, we need to keep track of the next and previous items accordingly. The best way to do so is to have a state for each one:

// usePosition.js export function usePosition(ref) { const [prevElement, setPrevElement] = useState(null) const [nextElement, setNextElement] = useState(null) }

The next step is to create a function that detects the position of the elements and updates the buttons to either hide or display depending on that position.

Let’s call it the update function. We’re gonna put it into React’s useEffect hook because, initially, we want to run this function when the DOM mounts the first time. We need access to our scrollable container which is available to use under the ref.current property. We’ll put it into a separate variable called element and start by getting the element’s position in the DOM.

We’re gonna use getBoundingClientRect() here as well. This is a very helpful function because it gives us an element’s position in the viewport (i.e. window) and allows us to proceed with our calculations.

// usePosition.js useEffect(() => { // Our scrollable container const element = ref.current const update = () => { const rect = element.getBoundingClientRect() }, [ref])

We’ve done a heck of a lot positioning so far and getBoundingClientRect() can help us understand both the size of the element — rect in this case — and its position relative to the viewport.

Credit: Mozilla Developer Network

The following step is a bit tricky as it requires a bit of math to calculate which elements are visible inside the container.

First, we need to filter each item by getting its position in the viewport and checking it against the container boundaries. Then, we check if the child’s left boundary is bigger than the container’s left boundary, and the same thing on the right side.

If one of these conditions is met means that our child is visible inside the container. Let’s convert it into the code step-by-step:

  1. We need to loop and filter through all container children. We can use the children property available on each node. So, let’s convert it into an array and filter:
const visibleElements = Array.from(element.children).filter((child) => {}
  1. After that, we need to get the position of each element by using that handy getBoundingClientRect() function once again:
const childRect = child.getBoundingClientRect()
  1. Now let’s bring our drawing to life:
rect.left <= childRect.left && rect.right >= childRect.right

Pulling that together, this is our script:

// usePosition.js const visibleElements = Array.from(element.children).filter((child) => { const childRect = child.getBoundingClientRect() return rect.left <= childRect.left && rect.right >= childRect.right })

Once we’ve filtered out items, we need to check whether an item is the first or the last one so we know to hide the left or right button accordingly. We’ll create two helper functions that check that condition using previousElementSibling and nextElementSibling. This way, we can see if there is a sibling in the list and whether it’s an HTML instance and, if it is, we will return it.

To receive the first element and return it, we need to take the first item from our visible items list and check if it contains the previous node. We’ll do the same thing for the last element in the list, however, we need to get the last item in the list and check if it contains the next element after itself:

// usePosition.js function getPrevElement(list) { const sibling = list[0].previousElementSibling if (sibling instanceof HTMLElement) { return sibling } return sibling } function getNextElement(list) { const sibling = list[list.length - 1].nextElementSibling if (sibling instanceof HTMLElement) { return sibling } return null }

Once we have those functions, we can finally check if there are any visible elements in the list, and then set our left and right buttons into the state:

// usePosition.js if (visibleElements.length > 0) { setPrevElement(getPrevElement(visibleElements)) setNextElement(getNextElement(visibleElements)) }

Now we need to call our function. Moreover, we want to call this function each time we scroll through the list — that’s when we want to detect the position of the element.

// usePosition.js export function usePosition(ref) { const [prevElement, setPrevElement] = useState(null) const [nextElement, setNextElement] = useState(null) useEffect(() => { const element = ref.current const update = () => { const rect = element.getBoundingClientRect() const visibleElements = Array.from(element.children).filter((child) => { const childRect = child.getBoundingClientRect() return rect.left <= childRect.left && rect.right >= childRect.right }) if (visibleElements.length > 0) { setPrevElement(getPrevElement(visibleElements)) setNextElement(getNextElement(visibleElements)) } } update() element.addEventListener('scroll', update, {passive: true}) return () => { element.removeEventListener('scroll', update, {passive: true}) } }, [ref])

Here’s an explanation for why we’re passing {passive: true} in there.

Now let’s return those properties from the hook and update our buttons accordingly:

// usePosition.js return { hasItemsOnLeft: prevElement !== null, hasItemsOnRight: nextElement !== null, } // Carousel.js <LeftCarouselButton hasItemsOnLeft={hasItemsOnLeft}> <ArrowLeft /> </LeftCarouselButton> <RightCarouselButton hasItemsOnRight={hasItemsOnRight}> <ArrowRight /> </RightCarouselButton> // Carousel.styled.js export const LeftCarouselButton = styled(CarouselButton)` left: 0; transform: translate(-100%, -50%); ${CarouserContainer}:hover & { transform: translate(0%, -50%); } visibility: ${({hasItemsOnLeft}) => (hasItemsOnLeft ? `all` : `hidden`)}; ` export const RightCarouselButton = styled(CarouselButton)` right: 0; transform: translate(100%, -50%); ${CarouserContainer}:hover & { transform: translate(0%, -50%); } visibility: ${({hasItemsOnRight}) => (hasItemsOnRight ? `all` : `hidden`)}; `

So far, so good. As you’ll see, our arrows show up dynamically depending on our scroll location in the list of items.

We’ve got just one final step to go to make the buttons functional. We need to create a function that’s gonna accept the next or previous element it needs to scroll to.

const scrollRight = useCallback(() => scrollToElement(nextElement), [ scrollToElement, nextElement, ]) const scrollLeft = useCallback(() => scrollToElement(prevElement), [ scrollToElement, prevElement, ])

Don’t forget to wrap functions into the useCallback hook in order to avoid unnecessary re-renders.

Next, we’ll implement the scrollToElement function. The idea is pretty simple. We need to take the left boundary of our previous or next element (depending on the button that’s clicked), sum it up with the width of the element, divided by two (center position), and offset this value by half of the container width. That will give us the exact scrollable distance to the center of the next/previous element.

Here’s that in code:

// usePosition.js const scrollToElement = useCallback( (element) => { const currentNode = ref.current if (!currentNode || !element) return let newScrollPosition newScrollPosition = element.offsetLeft + element.getBoundingClientRect().width / 2 - currentNode.getBoundingClientRect().width / 2 currentNode.scroll({ left: newScrollPosition, behavior: 'smooth', }) }, [ref], )

scroll actually does the scrolling for us while passing the precise distance we need to scroll to. Now let’s attach those functions to our buttons.

// Carousel.js const { hasItemsOnLeft, hasItemsOnRight, scrollRight, scrollLeft, } = usePosition(ref) <LeftCarouselButton hasItemsOnLeft={hasItemsOnLeft} onClick={scrollLeft}> <ArrowLeft /> </LeftCarouselButton> <RightCarouselButton hasItemsOnRight={hasItemsOnRight} onClick={scrollRight}> <ArrowRight /> </RightCarouselButton>

Pretty nice!

Like a good citizen, we ought to clean up our code a bit. For one, we can be more in control of the passed items with a little trick that automatically sends the styles needed for each child. The Children API is pretty rad and worth checking out.

<CarouserContainerInner ref={ref}> {React.Children.map(children, (child, index) => ( <CarouselItem key={index}>{child}</CarouselItem> ))} </CarouserContainerInner>

Now we just need to update our styled components. flex: 0 0 auto preserves the original sizes of the containers, so it’s totally optional

export const CarouselItem = styled('div')` flex: 0 0 auto; // Spacing between items margin-left: 1rem; ` export const CarouserContainerInner = styled(Flex)` overflow-x: scroll; scroll-snap-type: x mandatory; -ms-overflow-style: none; scrollbar-width: none; margin-left: -1rem; // Offset for children spacing &::-webkit-scrollbar { display: none; } ${CarouselItem} & { scroll-snap-align: center; } ` CodePen Embed Fallback Accessibility 

We care about our users, so we need to make our component not only functional, but also accessible so folks feel comfortable using it. Here are a couple things I’d suggest:

  • Adding role='region' to highlight the importance of this area.
  • Adding an area-label as an identifier.
  • Adding labels to our buttons so screen readers could easily identify them as “Previous” and “Next” and inform the user which direction a button goes.
// Carousel.js <CarouserContainer role="region" aria-label="Colors carousel"> <CarouserContainerInner ref={ref}> {React.Children.map(children, (child, index) => ( <CarouselItem key={index}>{child}</CarouselItem> ))} </CarouserContainerInner> <LeftCarouselButton hasItemsOnLeft={hasItemsOnLeft} onClick={scrollLeft} aria-label="Previous slide > <ArrowLeft /> </LeftCarouselButton> <RightCarouselButton hasItemsOnRight={hasItemsOnRight} onClick={scrollRight} aria-label="Next slide" > <ArrowRight /> </RightCarouselButton> </CarouserContainer> More than one carousel? No problem!

Feel free to add additional carousels to see how it behaves with the different size items. For example, let’s drop in a second carousel that’s just an array of numbers.

const numbersArray = Array.from(Array(10).keys()).map((number) => ( <Item size={5} style={{color: 'black'}} key={number}> {number} </Item> )) function App() { return ( <Container> <H1>Easy Carousel</H1> <HorizontalCenter> <Carousel>{colorsArray}</Carousel> </HorizontalCenter> <HorizontalCenter> <Carousel>{numbersArray}</Carousel> </HorizontalCenter> </Container> ) }

And voilà, magic! Dump a bunch of items and you’ve got fully workable carousel right out of the box.

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Feel free to modify this and use it in your projects. I sincerely hope that this is a good starting point to use as-is, or enhance it even further for a more complex carousel. Questions? Ideas? Contact me on Twitter, GitHub, or the comments below!

The post A Super Flexible CSS Carousel, Enhanced With JavaScript Navigation appeared first on CSS-Tricks.

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Through the pipeline: An exploration of front-end bundlers

Css Tricks - Thu, 03/04/2021 - 1:56pm

I really like the kind of tech writing where a fellow developer lays out some specific needs, tries out different tech to fulfill those needs, and documents how it went for them.

That’s exactly what Andrew Walpole did here. He wanted to try out bundlers in the context of WordPress themes and needing a handful of specific files built. Two JavaScript and two Sass files, which can import things from npm, and need to be minified with sourcemaps and all that. Essentially the same crap we were doing when I wrote Grunt for People Who Think Things Like Grunt are Weird and Hard eight years ago. The process hasn’t gotten any easier, but at least it’s gotten faster.

The winner for Andrew: esbuild through Estrella.

Direct Link to ArticlePermalink

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Weekly Platform News: Focus Rings, Donut Scope, More em Units, and Global Privacy Control

Css Tricks - Thu, 03/04/2021 - 11:33am

In this week’s news, Chrome tackles focus rings, we learn how to get “donut” scope, Global Privacy Control gets big-name adoption, it’s time to ditch pixels in media queries, and a snippet that prevents annoying form validation styling.

Chrome will stop displaying focus rings when clicking buttons

Chrome, Edge, and other Chromium-based browsers display a focus indicator (a.k.a. focus ring) when the user clicks or taps a (styled) button. For comparison, Safari and Firefox don’t display a focus indicator when a button is clicked or tapped, but do only when the button is focused via the keyboard.

The focus ring will stay on the button until the user clicks somewhere else on the page.

Some developers find this behavior annoying and are using various workarounds to prevent the focus ring from appearing when a button is clicked or tapped. For example, the popular what-input library continuously tracks the user’s input method (mouse, keyboard or touch), allowing the page to suppress focus rings specifically for mouse clicks.

[data-whatintent="mouse"] :focus { outline: none; }

A more recent workaround was enabled by the addition of the CSS :focus-visible pseudo-class to Chromium a few months ago. In the current version of Chrome, clicking or tapping a button invokes the button’s :focus state but not its :focus-visible state. that way, the page can use a suitable selector to suppress focus rings for clicks and taps without affecting keyboard users.

:focus:not(:focus-visible) { outline: none; }

Fortunately, these workarounds will soon become unnecessary. Chromium’s user agent stylesheet recently switched from :focus to :focus-visible, and as a result of this change, button clicks and taps no longer invoke focus rings. The new behavior will first ship in Chrome 90 next month.

The enhanced CSS :not() selector enables “donut scope”

I recently wrote about the A:not(B *) selector pattern that allows authors to select all A elements that are not descendants of a B element. This pattern can be expanded to A B:not(C *) to create a “donut scope.”

For example, the selector article p:not(blockquote *) matches all <p> elements that are descendants of an <article> element but not descendants of a <blockquote> element. In other words, it selects all paragraphs in an article except the ones that are in a block quotation.

The donut shape that gives this scope its name CodePen Embed Fallback The New York Times now honors Global Privacy Control

Announced last October, Global Privacy Control (GPC) is a new privacy signal for the web that is designed to be legally enforceable. Essentially, it’s an HTTP Sec-GPC: 1 request header that tells websites that the user does not want their personal data to be shared or sold.

The DuckDuckGo Privacy Essentials extension enables GPC by default in the browser

The New York Times has become the first major publisher to honor GPC. A number of other publishers, including The Washington Post and Automattic (WordPress.com), have committed to honoring it “this coming quarter.”

From NYT’s privacy page:

Does The Times support the Global Privacy Control (GPC)?

Yes. When we detect a GPC signal from a reader’s browser where GDPR, CCPA or a similar privacy law applies, we stop sharing the reader’s personal data online with other companies (except with our service providers).

The case for em-based media queries

Some browsers allow the user to increase the default font size in the browser’s settings. Unfortunately, this user preference has no effect on websites that set their font sizes in pixels (e.g., font-size: 20px). In part for this reason, some websites (including CSS-Tricks) instead use font-relative units, such as em and rem, which do respond to the user’s font size preference.

Ideally, a website that uses font-relative units for font-size should also use em values in media queries (e.g., min-width: 80em instead of min-width: 1280px). Otherwise, the site’s responsive layout may not always work as expected.

For example, CSS-Tricks switches from a two-column to a one-column layout on narrow viewports to prevent the article’s lines from becoming too short. However, if the user increases the default font size in the browser to 24px, the text on the page will become larger (as it should) but the page layout will not change, resulting in extremely short lines at certain viewport widths.

If you’d like to try out em-based media queries on your website, there is a PostCSS plugin that automatically converts min-width, max-width, min-height, and max-height media queries from px to em.

(via Nick Gard)

A new push to bring CSS :user-invalid to browsers

In 2017, Peter-Paul Koch published a series of three articles about native form validation on the web. Part 1 points out the problems with the widely supported CSS :invalid pseudo-class:

  • The validity of <input> elements is re-evaluated on every key stroke, so a form field can become :invalid while the user is still typing the value.
  • If a form field is required (<input required>), it will become :invalid immediately on page load.

Both of these behaviors are potentially confusing (and annoying), so websites cannot rely solely on the :invalid selector to indicate that a value entered by the user is not valid. However, there is the option to combine :invalid with :not(:focus) and even :not(:placeholder-shown) to ensure that the page’s “invalid” styles do not apply to the <input> until the user has finished entering the value and moved focus to another element.

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The CSS Selectors module defines a :user-invalid pseudo-class that avoids the problems of :invalid by only matching an <input> “after the user has significantly interacted with it.”

Firefox already supports this functionality via the :-moz-ui-invalid pseudo-class (see it in action). Mozilla now intends to un-prefix this pseudo-class and ship it under the standard :user-invalid name. There are still no signals from other browser vendors, but the Chromium and WebKit bugs for this feature have been filed.

The post Weekly Platform News: Focus Rings, Donut Scope, More em Units, and Global Privacy Control appeared first on CSS-Tricks.

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Exploring @property and its Animating Powers

Css Tricks - Thu, 03/04/2021 - 5:51am

Uh, what’s @property? It’s a new CSS feature! It gives you superpowers. No joke, there is stuff that @property can do that unlocks things in CSS we’ve never been able to do before.

While everything about @property is exciting, perhaps the most interesting thing is that it provides a way to specify a type for custom CSS properties. A type provides more contextual information to the browser, and that results in something cool: We can give the browser the information is needs to transition and animate those properties!

But before we get too giddy about this, it’s worth noting that support isn’t quite there. As it current stands at the time of this writing, @property is supported in Chrome and, by extension, Edge. We need to keep an eye on browser support for when we get to use this in other places, like Firefox and Safari.

First off, we get type checking @property --spinAngle { /* An initial value for our custom property */ initial-value: 0deg; /* Whether it inherits from parent set values or not */ inherits: false; /* The type. Yes, the type. You thought TypeScript was cool */ syntax: '<angle>'; } @keyframes spin { to { --spinAngle: 360deg; } }

That’s right! Type checking in CSS. It’s sorta like creating our very own mini CSS specification. And that’s a simple example. Check out all of the various types we have at our disposal:

  • length
  • number
  • percentage
  • length-percentage
  • color
  • image
  • url
  • integer
  • angle
  • time
  • resolution
  • transform-list
  • transform-function
  • custom-ident (a custom identifier string)

Before any of this, we may have relied on using “tricks” for powering animations with custom properties.

CSS variables are awesome, right? But scope power is often overlooked. For example, take this demo, 3 different animations but only 1 animation defined &#x1f4aa; That means dynamic animations &#x1f60e; https://t.co/VN02NlC4G8 via @CodePen #CSS #animation #webdev #webdesign #coding pic.twitter.com/ig8baxr7F3

— Jhey &#x1f43b;&#x1f6e0; (@jh3yy) November 5, 2019

What cool stuff can we do then? Let’s take a look to spark our imaginations.

Let’s animate color

How might you animate an element either through a series of colors or between them? I’m a big advocate for the HSL color space which breaks things down into fairly understandable numbers: hue, saturation, and lightness, respectively.

Animating a hue feels like something fun we can do. What’s colorful? A rainbow! There’s a variety of ways we could make a rainbow. Here’s one:

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In this example, CSS Custom Properties are set on the different bands of the rainbow using :nth-child() to scope them to individual bands. Each band also has an --index set to help with sizing.

To animate those bands, we might use that --index to set some negative animation delays, but then use the same keyframe animation to cycle through hues.

.rainbow__band { border-color: hsl(var(--hue, 10), 80%, 50%); animation: rainbow 2s calc(var(--index, 0) * -0.2s) infinite linear; } @keyframes rainbow { 0%, 100% { --hue: 10; } 14% { --hue: 35; } 28% { --hue: 55; } 42% { --hue: 110; } 56% { --hue: 200; } 70% { --hue: 230; } 84% { --hue: 280; } }

That might work out okay if you want a “stepped” effect. But, those keyframe steps aren’t particularly accurate. I’ve used steps of 14% as a rough jump.

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We could animate the border-color and that would get the job done. But, we’d still have a keyframe step calculation issue. And we need to write a lot of CSS to get this done:

@keyframes rainbow { 0%, 100% { border-color: hsl(10, 80%, 50%); } 14% { border-color: hsl(35, 80%, 50%); } 28% { border-color: hsl(55, 80%, 50%); } 42% { border-color: hsl(110, 80%, 50%); } 56% { border-color: hsl(200, 80%, 50%); } 70% { border-color: hsl(230, 80%, 50%); } 84% { border-color: hsl(280, 80%, 50%); } }

Enter @property. Let’s start by defining a custom property for hue. This tells the browser our custom property, --hue, is going to be a number (not a string that looks like a number):

@property --hue { initial-value: 0; inherits: false; syntax: '<number>'; }

Hue values in HSL can go from 0 to 360. We start with an initial value of 0. The value isn’t going to inherit. And our value, in this case, is a number. The animation is as straightforward as:

@keyframes rainbow { to { --hue: 360; } }

Yep, that’s the ticket:

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To get the starting points accurate, we could play with delays for each band. This gives us some cool flexibility. For example, we can up the animation-duration and we get a slow cycle. Have a play with the speed in this demo.

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It may not be the “wildest” of examples, but I think animating color has some fun opportunities when we use color spaces that make logical use of numbers. Animating through the color wheel before required some trickiness. For example, generating keyframes with a preprocessor, like Stylus:

@keyframes party for $frame in (0..100) {$frame * 1%} background 'hsl(%s, 65%, 40%)' % ($frame * 3.6)

We do this purely because this isn’t understood by the browser. It sees going from 0 to 360 on the color wheel as an instant transition because both hsl values show the same color.

@keyframes party { from { background: hsl(0, 80%, 50%); } to { background: hsl(360, 80%, 50%); } }

The keyframes are the same, so the browser assumes the animation stays at the same background value when what we actually want is for the browser to go through the entire hue spectrum, starting at one value and ending at that same value after it goes through the motions.

Think of all the other opportunities we have here. We can:

  • animate the saturation
  • use different easings
  • animate the lightness
  • Try rgb()
  • Try degrees in hsl() and declare our custom property type as <angle>

What’s neat is that we can share that animated value across elements with scoping! Consider this button. The border and shadow animate through the color wheel on hover.

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Animating color leads me think… wow!

CodePen Embed Fallback Straight-up numbering

Because we can define types for numbers—like integer and number—that means we can also animate numbers instead of using those numbers as part of something else. Carter Li actually wrote an article on this right here on CSS-Tricks. The trick is to use an integer in combination with CSS counters. This is similar to how we can work the counter in “Pure CSS” games like this one.

The use of counter and pseudo-elements provides a way to convert a number to a string. Then we can use that string for the content of a pseudo-element. Here are the important bits:

@property --milliseconds { inherits: false; initial-value: 0; syntax: '<integer>'; } .counter { counter-reset: ms var(--milliseconds); animation: count 1s steps(100) infinite; } .counter:after { content: counter(ms); } @keyframes count { to { --milliseconds: 100; } }

Which gives us something like this. Pretty cool.

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Take that a little further and you’ve got yourself a working stopwatch made with nothing but CSS and HTML. Click the buttons! The rad thing here is that this actually works as a timer. It won’t suffer from drift. In some ways it may be more accurate than the JavaScript solutions we often reach for such as setInterval. Check out this great video from Google Chrome Developer about JavaScript counters.

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What other things could you use animated numbers for? A countdown perhaps?

Animated gradients

You know the ones, linear, radial, and conic. Ever been in a spot where you wanted to transition or animate the color stops? Well, @property can do that!

Consider a gradient where we‘re creating some waves on a beach. Once we’ve layered up some images we could make something like this.

body { background-image: linear-gradient(transparent 0 calc(35% + (var(--wave) * 0.5)), var(--wave-four) calc(75% + var(--wave)) 100%), linear-gradient(transparent 0 calc(35% + (var(--wave) * 0.5)), var(--wave-three) calc(50% + var(--wave)) calc(75% + var(--wave))), linear-gradient(transparent 0 calc(20% + (var(--wave) * 0.5)), var(--wave-two) calc(35% + var(--wave)) calc(50% + var(--wave))), linear-gradient(transparent 0 calc(15% + (var(--wave) * 0.5)), var(--wave-one) calc(25% + var(--wave)) calc(35% + var(--wave))), var(--sand); }

There is quite a bit going on there. But, to break it down, we’re creating each color stop with calc(). And in that calculation, we add the value of --wave. The neat trick here is that when we animate that --wave value, all the wave layers move.

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This is all the code we needed to make that happen:

body { animation: waves 5s infinite ease-in-out; } @keyframes waves { 50% { --wave: 25%; } }

Without the use of @property, our waves would step between high and low tide. But, with it, we get a nice chilled effect like this.

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It’s exciting to think other neat opportunities that we get when manipulating images. Like rotation. Or how about animating the angle of a conic-gradient… but, within a border-image. Bramus Van Damme does a brilliant job covering this concept.

Let’s break it down by creating a charging indicator. We’re going to animate an angle and a hue at the same time. We can start with two custom properties:

@property --angle { initial-value: 0deg; inherits: false; syntax: '<number>'; } @property --hue { initial-value: 0; inherits: false; syntax: '<angle>'; }

The animation will update the angle and hue with a slight pause on each iteration.

@keyframes load { 0%, 10% { --angle: 0deg; --hue: 0; } 100% { --angle: 360deg; --hue: 100; } }

Now let’s apply it as the border-image of an element.

.loader { --charge: hsl(var(--hue), 80%, 50%); border-image: conic-gradient(var(--charge) var(--angle), transparent calc(var(--angle) * 0.5deg)) 30; animation: load 2s infinite ease-in-out; }

Pretty cool.

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Unfortunately, border-image doesn‘t play nice with border-radius. But, we could use a pseudo-element behind it. Combine it with the number animation tricks from before and we’ve got a full charging/loading animation. (Yep, it changes when it gets to 100%.)

CodePen Embed Fallback Transforms are cool, too

One issue with animating transforms is transitioning between certain parts. It often ends up breaking or not looking how it should. Consider the classic example of a ball being throw. We want it to go from point A to point B while imitating the effect of gravity.

An initial attempt might look like this

@keyframes throw { 0% { transform: translate(-500%, 0); } 50% { transform: translate(0, -250%); } 100% { transform: translate(500%, 0); } }

But, we’ll soon see that it doesn’t look anything like we want.

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Before, we may have reached for wrapper elements and animated them in isolation. But, with @property, we can animate the individual values of the transform. And all on one timeline. Let’s flip the way this works by defining custom properties and then setting a transform on the ball.

@property --x { inherits: false; initial-value: 0%; syntax: '<percentage>'; } @property --y { inherits: false; initial-value: 0%; syntax: '<percentage>'; } @property --rotate { inherits: false; initial-value: 0deg; syntax: '<angle>'; } .ball { animation: throw 1s infinite alternate ease-in-out; transform: translateX(var(--x)) translateY(var(--y)) rotate(var(--rotate)); }

Now for our animation, we can compose the transform we want against the keyframes:

@keyframes throw { 0% { --x: -500%; --rotate: 0deg; } 50% { --y: -250%; } 100% { --x: 500%; --rotate: 360deg; } }

The result? The curved path we had hoped for. And we can make that look different depending on the different timing functions we use. We could split the animation into three ways and use different timing functions. That would give us different results for the way the ball moves.

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Consider another example where we have a car that we want to drive around a square with rounded corners.

CodePen Embed Fallback

We can use a similar approach to what we did with the ball:

@property --x { inherits: false; initial-value: -22.5; syntax: '<number>'; } @property --y { inherits: false; initial-value: 0; syntax: '<number>'; } @property --r { inherits: false; initial-value: 0deg; syntax: '<angle>'; }

The car’s transform is using calculated with vmin to keep things responsive:

.car { transform: translate(calc(var(--x) * 1vmin), calc(var(--y) * 1vmin)) rotate(var(--r)); }

Now can write an extremely accurate frame-by-frame journey for the car. We could start with the value of --x.

@keyframes journey { 0%, 100% { --x: -22.5; } 25% { --x: 0; } 50% { --x: 22.5; } 75% { --x: 0; } }

The car makes the right journey on the x-axis.

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Then we build upon that by adding the travel for the y-axis:

@keyframes journey { 0%, 100% { --x: -22.5; --y: 0; } 25% { --x: 0; --y: -22.5; } 50% { --x: 22.5; --y: 0; } 75% { --x: 0; --y: 22.5; } }

Well, that’s not quite right.

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Let’s drop some extra steps into our @keyframes to smooth things out:

@keyframes journey { 0%, 100% { --x: -22.5; --y: 0; } 12.5% { --x: -22.5; --y: -22.5; } 25% { --x: 0; --y: -22.5; } 37.5% { --y: -22.5; --x: 22.5; } 50% { --x: 22.5; --y: 0; } 62.5% { --x: 22.5; --y: 22.5; } 75% { --x: 0; --y: 22.5; } 87.5% { --x: -22.5; --y: 22.5; } }

Ah, much better now:

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All that‘s left is the car‘s rotation. We‘re going with a 5% window around the corners. It’s not precise but it definitely shows the potential of what’s possible:

@keyframes journey { 0% { --x: -22.5; --y: 0; --r: 0deg; } 10% { --r: 0deg; } 12.5% { --x: -22.5; --y: -22.5; } 15% { --r: 90deg; } 25% { --x: 0; --y: -22.5; } 35% { --r: 90deg; } 37.5% { --y: -22.5; --x: 22.5; } 40% { --r: 180deg; } 50% { --x: 22.5; --y: 0; } 60% { --r: 180deg; } 62.5% { --x: 22.5; --y: 22.5; } 65% { --r: 270deg; } 75% { --x: 0; --y: 22.5; } 85% { --r: 270deg; } 87.5% { --x: -22.5; --y: 22.5; } 90% { --r: 360deg; } 100% { --x: -22.5; --y: 0; --r: 360deg; } }

And there we have it, a car driving around a curved square! No wrappers, no need for complex Math. And we composed it all with custom properties.

CodePen Embed Fallback Powering an entire scene with variables

We‘ve seen some pretty neat @property possibilities so far, but putting everything we’ve looked at here together can take things to another level. For example, we can power entire scenes with just a few custom properties.

Consider the following concept for a 404 page. Two registered properties power the different moving parts. We have a moving gradient that’s clipped with -webkit-background-clip. The shadow moves by reading the values of the properties. And we swing another element for the light effect.

CodePen Embed Fallback That’s it!

It’s exciting to think about what types of things we can do with the ability to define types with @property. By giving the browser additional context about a custom property, we can go nuts in ways we couldn’t before with basic strings.

What ideas do you have for the other types? Time and resolution would make for interesting transitions, though I’ll admit I wasn’t able to make them work that way I was hoping. url could also be neat, like perhaps transitioning between a range of sources the way an image carousel typically does. Just brainstorming here!

I hope this quick look at @property inspires you to go check it out and make your own awesome demos! I look forward to seeing what you make. In fact, please share them with me here in the comments!

The post Exploring @property and its Animating Powers appeared first on CSS-Tricks.

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How to Develop and Test a Mobile-First Design in 2021

Css Tricks - Thu, 03/04/2021 - 5:49am

The internet has connected 4.66 billion people with each other as of October 2020. A total of 59% of the world’s total population. Amazingly, this is not even the surprising part. The stat to look out for is mobile users and their rise in the internet world. Out of 4.66 billion people connected to the internet, 4.28 billion are mobile internet users. A number that reminds us of how vital mobile users are and why we need to keep them on priority. As surprising as these numbers are, everyone saw this coming with the sudden rise in mobile users and mobile sales all around the world. As a web developer, we have been prepared in shifting our design methodologies and development tactics according to mobile users for some time now. One such design paradigm is the mobile-first design which is a witness to our commitment to mobile internet users all around the world. A design strategy that starts with mobile users and works around their interest. This post takes the mobile-first design into the centre and explores the complexities of mobile-first design development and testing and how it affects our business in a positive way.

What is a Mobile-First Design?

Mobile-first design is the process of planning and developing a website keeping in mind the mobile-users first. This methodology of development changed from desktop-first, which has always been the way, reacting to the surge in mobile internet users around the world. Mobile-first design is a part of progressive advancement method in which we progress towards more advance design slowly.

Progressive advancement starts from a basic design fulfilling the requirements of the mobile device. This basic design consists of minimal elements on the webpage eliminating everything that a mobile user is not interested in. From here, we take another step and add a few more elements increasing the complexity of our design while sticking to the modern web design techniques and mobile-friendliness. This goes on until we are satisfied and have implemented all the necessary modules in our application.

Credit: Smartz

Mobile-first design is a practice of starting the development with respect to the mobile user or a mobile device first. Contributing 52% of the internet traffic today, a mobile-first website can help us lift the overall engagement and make us visible on the internet (on Google). With the start of mobile-first indexing, Google has also twisted their algorithm to show that mobile users are the priority today. Mobile-first design is not a complex task but a series of small development changes that can help your website render perfectly on the mobile with a happy user. To develop a mobile-first design website, we need to absorb some habits and remember a few tips to test the application efficiently.

How To Develop a Mobile-First Design

The journey of developing a mobile-first design can be roughly divided into the following stages:


Wireframe’s importance in a mobile-first design is similar to a map when we construct a new building. Wireframe provides an architectural way of how things are going to be. With wireframes in hand, not only technical teams, everyone related to the project can understand the high-level view of the application or in user’s terms: how will my application look?

While clients and analysts can tick mark their checklist of requirements, developers can understand how the elements will be laid down on to the application.

Credit: Balsamiq

A research paper published by KPMG, determining “Unsuccessful Information Technology Projects” revealed poor project planning as one of the reasons for project failure. The other good reason to use wireframes is that they increase the efficiency of the developers because of the clearer objectives. A similar result can be seen with TDD and BDD approach in testing.

Use Responsiveness and A Responsive Framework

A responsive framework is a crucial step in mobile-first design development. A responsive website adjusts itself with the environment it is rendered on such as screen size, platform or orientation. Mobile devices do not have a fixed size in the market. An overwhelming list on Screensiz will make you believe that applying media queries and meta tag will not work for all the devices and a generic approach is the only solution. Responsiveness is not only adjusting to the screen of the device, but also to the user’s experience. For example, images are an important part of a web page. Even though a user may skim the content, they will glance at an image at least once. It needs to be perfect! But while shrinking the aspect ratio of the webpage, we unknowingly focus out the image subject from the image. In the following image, the comparison speaks this point as the family becomes out of focus on a smaller screen device:

Simply resizing is a risky business as an image may lose its importance altogether. A good responsive website takes care of this aspect and render a different lower quality but cropped image on a smaller screen as below:

Or if I just show the mobile image, it has been cropped to as follows:

Since the focus is not the tree but the family, we need the users to see our subject with clarity. This is a responsive nature according to the user experience which is a part of a responsive website.

A responsive framework keeps the responsive needs in mind and has built-in capabilities to enhance the responsiveness of the website. With a responsive framework, the developers need not take care of every little thing and can focus on major issues such as the image resizing shown above. Responsive frameworks are more successful and popular in a mobile-first design strategy.

Follow the thumb rule

Before placing our content on the web page, we have to decide the location of each element with respect to the interaction habits of mobile users. A simple reason for this thought is the generic way most people use their phone; with one hand.

75% of people use their thumb to operate the mobile device which when painted as a red-green zone looks as follows:

Credit: Biracial Booty

The green zone in the above image shows the easily accessible area on a mobile screen. Our most important elements, such as CTAs, should reside in the green zone for a mobile-user to access easily. Remember that the user is not using a mouse to operate a mobile device. Reaching the red zone will take efforts and repeated actions of which, voluntarily or involuntarily, a user always notices.

The below-given image shows the efforts a user would have to take with a very small design change (which in my way, is not a mobile-first design):

Credit: Ranjith Manoharan

This small change can lead to increased user engagement demanding no efforts from our user.

Untangle Your Mobile-First Content and Design

Designing a web page desktop-style demands no extra attention towards the content. The screen is big and can accommodate whatever content you wish to add. The same attitude does not work in a mobile-first way. When the screen is smaller and we have only less than 3 seconds to impress a user, the content needs to be concise and to the point. A good solution to replace a lot of content from your screen is to use images, a hierarchical method of design or through a better user interface.

The content thoughts are to be replicated when we work with elements in a mobile-first design for the same reason of lesser screen space. Providing a congested screen with too many elements spread throughout confuses a user and slides him away from the CTA conversion goal. This is also called a minimalistic approach (or minimalism) in web design. A minimalistic approach distributes too few elements on to the screen leaving out a considerable white space for the user. The following image shows the minimalistic design:

Credit: Johnyvino

But a mobile design is different from a mobile-first design. Eventually, we would have to extend this web page for the desktop users too. Minimalism on the desktop is also a good approach given that the font-size and hero images are equally proportionate.

Decluttering our design and content reminds us why it is important to move from basic to advanced and not vice-versa (also called graceful degradation). Had it been the desktop design at the start, the team has to conduct the brainstorm sessions first to fill a large screen and then removing them one by one for the mobile device. By that time, management becomes too complex, hard to confine our elements and takes too much time and efforts. Therefore, start basic with a minimal design and then move forward which is the initial step in a mobile-first design strategy.

Prioritize UI and UX

A mobile-first design needs to revolve around mobile users to increase engagements and conversions on our web application. While animations and transitions are as fancy to look as to touch, the user experience is much more than explicit elements. Our user experience need not be too ostentatious but should engage the users without them realising our intentions. For example, elements should be extremely easy to find on a web page. A mobile user should never struggle to find the search button Conventional locations of the elements work in this case such as a navigation bar is always expected to be in the corner (left or right).

Another aspect in prioritizing the user experience is to enlarge the touch targets for comfortable interaction. Unlike a desktop with a small pointed arrow, we touch our screens with our thumbs which require a considerable large area. A mobile-first design encourages large clickable elements with white space between them to avoid unwanted clicks.

It is not a bad idea to keep these parameters intact while progressing towards the desktop side. Businesses have started to keep a better UI including large boxes to touch on desktops as well which shows their mobile-first design approach clearly. Enlarging elements also include determining the best font-size for your web page considering the smaller screen size. Font-size are easier to switch through media queries and you can follow the following chart to decide which size to go for in which scenario:

Credit: Airbus

Remember that font-type also affects the font-size visibility and readability on a mobile device. Therefore, it is better to test and find your perfect size taking the above chart for reference.

Tip: A small thing to remember in developing a mobile-first design is to avoid hover-only elements on your web page. Hovering is a great tool on desktops but mobiles do not have any support for hover. They work on touch interaction. You can keep the hover design along with the touch facility but constructing elements only with hover property is not a good idea.

CTA Placement

CTA is an important button. It helps in conversion goals and every business wants its users to click that button and increase their conversion rate. Therefore it demands special attention from the team members. The location of the CTA is the first thing that should be finalised carefully reminding yourself not to let our user work too hard.

CTAs should always be in the reach of the thumb (remember the green zone?) and on the first presented screen (above the fold) as well.

Apart from CTA placement, the message and presentation of a CTA is also an art in itself but let’s leave that for mobile-friendliness discussions.

Navigation Bar

The navigation bar on a mobile-first design needs simplification more than the desktop ones. While the desktop design has also transformed navigation bars into different unique designs, mobile-first is still enjoying the conventional hamburger menu style. People expect that today! If a user cannot find an option on the landing screen, he looks for those three horizontal lines that he knows will take him to what he is looking for.

The following image shows LambdaTest transformation of the navigation bar on two different devices:

The mobile-first approach helps us in shrinking down the available links on the navigation menu as long lists of links are not appreciated well. For those who cannot sacrifice, a nested layout seems a better choice than intimidating the user with a long list of links. In addition, it also keeps our presentation clean and encourages minimal design with decluttered content approach.

Say No To Heavy Elements

A web page’s loading speed has become a make or breaks parameter in website designing. An Unbounce survey shows that 70% of the customers are influenced by a website’s speed. Their decisions are affected by the FCP or full page load. Rendering the FCP (the first thing visible on your website) is a better choice as the user has something to get engaged in.

Google recommends a loading time of 2 seconds and under. Currently, the majority of these websites do not follow this criteria. As much as 57% of peopleleave a website that takes more than three seconds to load. The conversion rates also take a toll when the page speed is higher than expected affecting business directly. So, how can we save ourselves from this?

Using lighter elements on a web page crafted for mobile users is the first step to go for. If images exist, they probably should be in a lossless algorithm format such as JPEG and of lower size. Resizing them to a lower ratio helps too since the mobile user is rarely concerned about high-quality images apart from the product images. Using CDNs can also help in decreasing the page load time. For a WordPress website, plugins should be as minimal and light-weight as possible. Static plugins are a good start but eventually, the elements on a web page should be lighter, using asynchronous algorithms for FCP and should make fewer requests to the server.

How to test a mobile-first design?

The above points assist us during the development of a mobile-first design that starts with a basic minimal design for the mobile user and increases the complexities without hindering the user experience. But an equally important aspect of a web application is testing it. Testing an application can point out hidden bugs and functionalities that either is not liked by the people or behave inappropriately. Let’s check out how we can go ahead and polish our mobile-first website by testing it.

Use Tools

Similar to using responsive frameworks in the development which gives us in-built functionality and takes care of common code, tools do the same in testing. A mobile web testing tool not only creates an environment for the website to render as, on a mobile device, but it also provides certain features that are extremely important for a mobile-first design.

Consider one such tool LT browser I recently discovered on ProductHunt.

LT Browser is a browser made specifically for mobile web testing and responsive testing of the website. It provides 45+ screen sizes for the testers to render their website on. With such a tool, you can easily find bugs using in-built debuggers and leverage hot reload features to help you in development as well. With built-in integrations and performance reports, you can analyze the performance and share it with your teammates easily.

LT Browser showing two devices side-by-side with different orientations

Test & Debug on the go – Using LT Browser users can test and debug their websites on the go, its in-built developer’s tool really comes in handy to make a website seamless across devices.

Network Throttling: This is an amazing and unique feature offered by LT Browser utilizing which a user can check how the website performs under high and low network bandwidth.

Local Testing: Local testing allows the developer to test their website even before pushing their website online. With the local tunnel, they can view the website on any of the 45+ devices from their local system.

Performance Report: To analyse the final website performance, developers and testers can view the google lighthouse based performance report that will help them change certain website aspect in order to score more both on mobile and desktop devices.

Tools help you increase productivity and keep you efficient during the process. The choice of tools is the personal choice of the tester but they definitely should play a part in the overall testing.

Cross-Browser Testing

Cross-browser testing is the process of analyzing your website on different target browsers, operating systems and resolutions. For a mobile-friendly website to be successful, it should render as intended on a mobile screen without worrying about the platform and browser used. This can be tested through cross-browser tools like LambdaTest

As a tester and a developer, it is definitely not a good idea to take these efforts manually. There is an overwhelming number of OS, browser and resolution combinations that will take too much efforts to install and test. A better way is to go for online cross-browser testing tools with mobile browser and OS support or a mobile-specific browser like LT Browser discussed above.

So, what are we looking for in a cross-browser testing process?

Cross-browser testing looks for issues with the elements of a web page and whether they are supported or not. While functionality testing is another segment of testing, cross-browser testing points out the cross-browser compatibility issues. For example, if you have used CSS subgrids on the web page, they might not render on Google Chrome version 62. The same goes for Javascript libraries and other code. With a browser matrix in our hand, we can rest assured after performing the testing that our user will not be confused as he would when an element crashes on the webpage.

Validate HTML and CSS code

Every mishap on the web page is not the browser’s fault, sometimes programmers commit mistakes too! Since a web page is rendered or parsed by the browser and not compiled, errors and warnings do not stop a web page from loading. Now we have performed cross-browser testing but still cannot find an issue with a missing element is generally a wrong syntax fault. Such syntax errors and not following the W3C web standards can land us in trouble when we progress from mobile-first to complete desktop designs.

HTML and CSS code is very easy to validate. There are a lot of tools available which can do this job for us. Some of them are Validator.nu, W3CMarkup Validator and W3C CSS Validator.

Network Performance

In our efforts to test the page load speed of the web page, a major hurdle is a network. A slower network means slower downloading of web pages and more page load time. For a mobile-first design, it is extremely important to cover all types of users while performing the testing. One such section is the users with slower networks such as 3G network constituting 12% of North American internet users. Only 4% of people use the 5G network in North America now. Imagine this number for countries with poor network infrastructures!!

Network performance can be tested on a real device by switching the connections or through an online tool that provides such features. LT Browser has a network throttling feature to test the website on different connections which helps while performing responsive or cross-browser testing.

A/B Testing

A/B Testing is a type of variation testing or split testing that shows different variations of a web page to different segments of users. Website owners then analyze the performance of both versions and choose the better performing one. For a mobile-first design application, we may develop everything perfectly following every rule in the textbook but the final verdict is up to the user. If the user is not pressing that shiny CTA button, we need to fix that by knowing what the user wants.

A popular question in A/B testing is, where do we create the variation? We cannot jumble up every element on the web page and create fifty variations for the users. This can have an adverse impact on the business. To understand where we are going wrong and which elements need adjustments we can choose the Heatmap features. Heatmap allows the web app owners to see the user’s engagement with the web page and which part are they ignoring.

A famous case study of A/B testing includes the 40% improved sales on a varying page of EA Sports’ SimCity 5 from this:

To this:

Buyers were least interested in the pre-order offer I guess!!

Usability Testing

The final step in completing our mobile-first web design is to present it to real-users and take their feedback. A/B testing is good, but even if you see the Heatmap of the web page, you cannot talk to a real user and ask them why are they not pressing the CTA button? Usability testing covers this hole.

Usability testing is performed with the real users who should be the target audience of the application. For example, you cannot ask a poet to check out a coding website right? Once these users are selected, we ask them to either record their session, their screens and speak their thoughts out loud. Sometimes, the testers can sit with the users too and make their notes by asking the questions. Sometimes, we can just ask them to fill a form with various options. Whatever way you do, usability testing is important and uncovers hidden bugs that are hard to find in a mobile-first design which is a tricky business in itself.

Why does mobile presence matter?

Our analysis of mobile-first design and its development techniques will make you wonder, why should I do mobile-first design? Does mobile presence matter that much?

A few days ago, I was going through my website on Google Search Console and the popped up message was the following:

Mobile-first design is so important today that Google considers mobile-first indexing as the primary search index technique and increasing the visibility on mobile searches which constitutes 52% of the internet traffic!! But this is from Google’s side, what do we have in the box for us?

Better Google Ranking

A mobile-first design is mobile-friendly. It is for mobile users. Therefore, Google realizes that we have a website that is perfect for a mobile user and makes us more visible on queries generated from a smartphone. As a result, our rankings improve. Better Google ranking attracts other businesses as we are more visible and can advertise for them on our website if we want. Since users generally do not remember the web site’s name, a Google search will help us generate traffic and conversions.

Higher Conversion Rates

A mobile-first design will ensure a decrease in the bounce rate. When bounce rates are low and people are actually interested in your website, they will stick to it and will also return back often. Given that the CTA is positioned right with all the eligibility criteria satisfied, a mobile-first design will push your conversion rates higher directly generating a better engagement and goal establishments. As a result, you will get a steady business from your application.

Large Audience Coverage

Businesses also generate a large audience base when they are visible on the Google rankings and have built a mobile-first design. A large audience base is the strength of any business. They require lesser efforts to be engaged as the trust has been established. On the other hand, seeing a larger involvement with your application, you can also introduce other features and services. Such a strong base is a marketing bonus for businesses.

Better Market Presence

Satisfying all the three requirements discussed above directly results in a better market presence. Even though mobile-first designs are recommended for every business, they are currently rare. Mobile-first design is yet to become a standard in web development and choosing it will keep you ahead in the race. A Google search keyword that shows your link in the query results increases your market presence among the competitors. They not only have to work harder to overtake you, but they might also need to restructure their designs if they are still working on desktop ones.

A better market presence means better word of mouth about your happenings, features and upcoming highlights. Such a presence is a direct cause for better revenues and a better future.

Is Mobile-First similar to Mobile-Responsive?

A short answer; no! Mobile-first is a design method. With the mobile-first design, we develop our web application for mobile users first. This starts from a very basic design and gradually advances towards a more complex design structure while keeping in view the mobile-friendliness and mobile users on priority. Mobile-first design is not a development technique but a design strategy that works as a catalyst in development. The developers can get a clear objective and work faster with the defined design.

Mobile-responsive is the ability of the website to adjust itself according to the mobile screen size. A mobile-responsive design need not start with the mobile version of the website and neither takes the thumb area or content relevance into account. Mobile-responsiveness is just concerned with rendering the website on a smaller device.

A mobile-responsive design strategy can be considered a part of the mobile-first design since to produce a mobile-first design, the application needs to be responsive in nature. The mobile-responsive design strategy was a good call when the mobile users had just started to increase. Today, there have been extensive researches on mobile designs in which a mobile-responsive design strategy is hard to survive. To cater to the needs of 4.2 billion mobile internet users, we need a mobile-first design.

Try LambdaTest

The post How to Develop and Test a Mobile-First Design in 2021 appeared first on CSS-Tricks.

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A Bare-Bones Approach to Versatile and Reusable Skeleton Loaders

Css Tricks - Wed, 03/03/2021 - 5:51am

UI components like spinners and skeleton loaders make waiting for a page load less frustrating and might even affect how loading times are perceived when used correctly. They won’t completely prevent users from abandoning the website, but they might encourage them to wait a bit longer. Animated spinners are used in most cases since they are easy to implement and they generally do a good enough job. Skeleton loaders have a limited use-case and might be complex to implement and maintain, but they offer an improved loading experience for those specific use-cases.

I’ve noticed that developers are either unsure when to use skeleton loaders to enhance the UX or do not know how to approach the implementation. More common examples of skeleton loaders around the web are not all that reusable or scalable. They are usually tailor-made for a single component and cannot be applied to anything else. That is one of the reasons developers use regular spinners instead and avoid the potential overhead in the code. Surely, there must be a way to implement skeleton loaders in a more simple, reusable, and scalable way.

Spinner elements and skeleton loaders

A spinner (or progress bar) element is the simplest and probably most commonly used element to indicate a loading state. A spinner might look better than a blank page, but it won’t hold user’s attention for long. Spinners tell the user that something will load eventually. Users have to passively wait for content to load, meaning that they are unable to interact with other elements on the page or consume any other content on the page. Spinners take up the entire screen space and no content is available to the user.

The spinner element is displayed and covers the entire screen until all content has finished loading.

However, skeleton loaders (or skeleton screens) tell the user that the content is about to load and they might provide a better loading UX than a simple spinner. Empty boxes (with a solid color or gradient background) are used as a placeholder for the content that is being loaded. In most cases, content is gradually being loaded which allows users to maintain a sense of progress and perception that a page load is faster than it is. Users are actively waiting, meaning that they can interact with the page or consume at least some part of the content while the rest is loading.

Empty boxes (with a solid color or gradient background) are used as a placeholder while content is being gradually loaded. Text content is loaded and displayed first, and images are loaded and displayed after that.

It’s important to note that loading components should not be used to address performance issues. If a website is experiencing performance issues due to the problem that can be addressed (un-optimized assets or code, back-end performance issues, etc.), they should be fixed first. Loading elements won’t prevent users from abandoning websites with poor performance and high loading times. Loading elements should be used as a last resort when waiting is unavoidable and when loading delay is not caused by unaddressed performance issues.

Using skeleton loaders properly

Skeleton loaders shouldn’t be treated as a replacement for full-screen loading elements but instead when specific conditions for content and layout have been met. Let’s take this step-by-step and see how to use loading UI components effectively and how to know when to go with skeleton loaders instead of regular spinners.

Is loading delay avoidable?

The best way to approach loading in terms of UX is to avoid it altogether. We need to make sure that loading delay is unavoidable and is not the result of the aforementioned performance issues that can be fixed. The main priority should always be performance improvements and reducing the time needed to fetch and display the content.

Is loading initiated by the user and is the feedback required?

In some cases, user actions might initiate additional content to load. Some examples include lazy-loading content (e.g. images) in the user’s viewport while scrolling, loading content on a button click, etc. We need to include a loading element for cases where a user needs to get some kind of feedback for their actions that have initiated the loading process.

As seen in the following mockup, without a loading element to provide feedback, a user doesn’t know that their actions have initiated any loading process that is happening in the background.

We are asynchronously loading the content in a modal when the button is clicked. In the first example, no loading element is displayed and users might think that their click hasn’t been registered. In the second example, users get the feedback that their click has been registered and that the content is being loaded. Is the layout consistent and predictable?

If we’ve decided to go with a loader element, we now need to choose what type of loader element best fits our use-case. Skeleton loaders are most effective in cases when we can predict the type and layout of the content that is being loaded in. If the skeleton loader layout doesn’t accurately represent the loaded content’s layout to some degree, the sudden change may cause layout shift and leave the user confused and disoriented. Use skeleton loaders for elements with predictable content for consistent layouts.

The grid layout on the left (taken from discogs.com) represents an ideal use-case for skeleton loaders, while the comments example on the right (taken from CSS-Tricks) is an ideal use-case for spinners. Is there content on the page that is immediately available to the user?

Skeleton loaders are most effective when there are sections or page elements already present on the page while the skeleton loader is active and additional content is actively loading. Gradually loading in content means that static content is available on page load and asynchronously-loaded content is displayed as it becomes available (for example, the first text is loaded and images after that). This approach ensures that the user maintains a sense of progression and is expecting the content to finish loading at any moment. Having the entire screen covered in skeleton loaders without any content present and without gradual content loading is not significantly better than having the screen covered by a full-page spinner or progress bar.

The mockup on the left shows a skeleton loader covering all elements until everything has loaded. The mockup on the right shows a skeleton loader covering only content that is being asynchronously loaded. The page is usable since they have a part of the website’s content displayed and the user maintains a sense of progression. Creating robust skeleton loaders

Now that we know when to use skeleton loaders and how to use them properly, we can finally do some coding! But first, let me tell you how we are going to approach this.

Most skeleton loading examples from around the web are, in my opinion, over-engineered and high-maintenance. You might have seen one of those examples where skeleton screens are created as a separate UI component with separate CSS styles or created with elaborate use of CSS gradients to simulate the final layout. Creating and maintaining a separate skeleton loader or skeleton styles for each UI component can become serious overhead in development with such a highly-specific approach. This is especially true when we look at scalability, as any change to the existing layout also involves updating the skeleton layout or styles.

Let’s try and find a bare-bones approach to implementing skeleton loading that should work for most use-cases and will be easy to implement, reuse and maintain!

Card grid component

We’ll use regular HTML, CSS, and JavaScript for implementation, but the overall approach can be adapted to work with most tech stacks and frameworks.

We are going to create a simple grid of six card elements (three in each row) as an example, and simulate asynchronous content loading with a button click.

We’ll use the following markup for each card. Notice that we are setting width and height on our images and using a 1px transparent image as a placeholder. This will ensure that the image skeleton loader is visible until the image has been loaded.

<div class="card"> <img width="200" height="200" class="card-image" src="..." /> <h3 class="card-title"></h3> <p class="card-description"></p> <button class="card-button">Card button</button> </div>

Here is our card grid example with some layout and presentation styles applied to it. Content nodes are added or removed from the DOM depending on the loading state using JavaScript to simulate asynchronous loading.

CodePen Embed Fallback Skeleton loader styles

Developers usually implement skeleton loaders by creating replacement skeleton components (with dedicated skeleton CSS classes) or by recreating entire layouts with CSS gradients. Those approaches are inflexible and not reusable at all since individual skeleton loaders are tailor-made for each layout. Considering that layout styles (spacings, grid, inline, block and flex elements, etc.) are already present from the main component (card) styles, skeleton loaders just need to replace the content, not the entire component!

With that in mind, let’s create skeleton loader styles that become active only when a parent class is set and use CSS properties that only affect the presentation and content. Notice that these styles are independent from the layout and content of the element they’re being applied to, which should make them highly reusable.

.loading .loading-item { background: #949494 !important; /* Customizable skeleton loader color */ color: rgba(0, 0, 0, 0) !important; border-color: rgba(0, 0, 0, 0) !important; user-select: none; cursor: wait; } .loading .loading-item * { visibility: hidden !important; } .loading .loading-item:empty::after, .loading .loading-item *:empty::after { content: "\00a0"; }

Base parent class .loading is used to activate the skeleton loading styles. The .loading-item class is used to override element’s presentational styles to display a skeleton element. This also ensures that the layout and dimensions of the element are preserved and inherited by the skeleton. Additionally, .loading-item makes sure that all child elements are hidden and have at least an empty space character (\00a0) inside it so that element is displayed and its layout is rendered.

Let’s add skeleton loader CSS classes to our markup. Notice how no additional HTML elements have been added, we are only applying additional CSS classes.

<div class="card loading"> <img width="200" height="200" class="card-image loading-item" src="..." /> <h3 class="card-title loading-item"></h3> <p class="card-description loading-item"></p> <button class="card-button loading-item">Card button</button> </div>

Once the content has loaded, we only need to remove loading CSS class from the parent component to hide the skeleton loader styles.

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These few lines should work for most, if not all, use cases depending on your custom CSS since these skeleton loaders inherit the layout from the main (content) styles and create a solid box that replaces the content by filling out the empty space left in the layout. We’re also applying these classes to non-empty elements (button with text) and replacing it with a skeleton. A button might have the text content ready from the start, but it might be missing additional data that is required for it to function correctly, so we should also hide it while that data is loaded in.

This approach can also adapt to most changes in the layout and markup. For example, if we were to remove the description part of the card or decide to move the title above the image, we wouldn’t need to make any changes to the skeleton styles, since skeleton responds to all changes in the markup.

Additional skeleton loading override styles can be applied to a specific element simply by using the .loading .target-element selector.

.loading .button, .loading .link { pointer-events: none; } Multi-line content and layout shifts

As you can see, the previous example works great with cards and the grid layout we’re using, but notice that the page content slightly jumps the moment it is loaded. This is called a layout shift. Our .card-description component has a fixed height with three lines of text, but the skeleton placeholder spans only one line of text. When the extra content is loaded, the container dimensions change and the overall layout is shifted as a result. Layout shift is not bad in this particular case, but might confuse and disorient the user in more severe cases.

This can be easily fixed directly in the placeholder element. Placeholder content is going to get replaced by the content that is being loaded anyway, so we can add anything we need inside it. So, let’s add a few <br /> elements to simulate multiple lines of text.

<div class="card loading"> <img width="200" height="200" class="card-image loading-item" src="..." /> <h3 class="card-title loading-item"></h3> <p class="card-description loading-item"><br/><br/><br/></p> <button class="card-button loading-item">Card button</button> </div>

We’re using basic HTML to shape the skeleton and change the number of lines inside it. Other examples on the web might achieve this using CSS padding or some other way, but this introduces overhead in the code. After all, content can span any number of lines and we would want to cover all those cases.

As an added benefit of using <br /> elements, they inherit the CSS properties that affect the content dimensions (e.g. the line height, font size, etc.). Similarly, &nbsp characters can be used to add additional spacing to the inline placeholder elements.

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With a few lines of CSS, we’ve managed to create versatile and extensible skeleton loader styles that can be applied to a wide range of UI components. We’ve also managed to come up with a simple way of vertically extending the skeleton boxes to simulate content that spans multiple lines of text.

To further showcase how versatile this skeleton loader CSS snippet is, I’ve created a simple example where I’ve added the snippet to a page using Bootstrap CSS framework without any additional changes or overrides. Please note that in this example no text content will be displayed or simulated, but it will work as in previous examples. This is just to showcase how styles can be easily integrated with other CSS systems.

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Here is an additional example to showcase how these styles can be applied to various elements, including input, label and a elements.

CodePen Embed Fallback Accessibility requirements

We should also take accessibility (a11y) requirements into account and make sure that the content is accessible to all users. Skeleton loaders without a11y features might disorientate and confuse users that have visual disabilities or browse the web using screen readers.


You might have noticed that the skeleton loaders in our example have a high contrast and they look more prominent compared to the common low-contrast skeleton loaders in the wild. Some users might experience difficulties perceiving and using low-contrast UI components. That is why Web Content Accessibility Guidelines (WCAG) specify a 3:1 minimum contrast for non-text UI components.

The upcoming “Media queries level 5” draft contains a prefers-contrast media query that will enable us to detect user contrast preferences. This will give us more flexibility by allowing us to assign a high-contrast background color to skeleton loaders for users that request a high-contrast version, and have a subtle low-contrast background color for others. I would suggest implementing high-contrast skeleton loaders by default until the prefers-contrast media query becomes more widely supported.

/* NOTE: as of the time of writing this article, this feature is not supported in browsers, so this code won't work */ .loading .loading-item { /* Default skeleton loader styles */ } @media (prefers-contrast: high) { .loading .loading-item { /* High-contrast skeleton loader styles */ } } Animations

Depending on the design and the implementation of animated skeleton loaders, users suffering from visual disorders might feel overwhelmed by the animations and find the site unusable. It’s always a good idea to prevent animations from firing for users that prefer reduced motion. This media query is widely-supported in modern browsers and can be used without any caveats.

.loading .loading-item { animation-name: skeleton; background: /* animated gradient background */; } @media (prefers-reduced-motion) { .loading .loading-item { animation: none !important; background: /* solid color */; } } Screen readers

To better support screen readers, we need to update our HTML with ARIA (Accessible Rich Internet Applications) markup. This markup won’t affect our content or presentation, but it will allow users using screen readers to better understand and navigate around our website content, including our skeleton loaders.

Adrian Roselli has very detailed research on the topic of accessible skeleton loaders for cases when skeleton loaders are implemented as separate UI components. For our example, I’ll use the aria-hidden attribute in combination with visually hidden text to give screen readers a hint that content is in the process of loading. Screen readers will ignore the content with aria-hidden="true", but they’ll use the visually-hidden element to indicate the loading state to the user.

Let’s update our cards with the ARIA markup and loading indicator element.

<div class="card loading"> <span aria-hidden="false" class="visually-hidden loading-text">Loading... Please wait.</span> <img width="200" height="200" class="card-image loading-item" aria-hidden="true" src="..." /> <h3 class="card-title loading-item" aria-hidden="true"></h3> <p class="card-description loading-item" aria-hidden="true"><br/><br/><br/></p> <button class="card-button loading-item" aria-hidden="true">Card button</button> </div>

We also could have applied aria-hidden to the grid container element and add a single visually hidden element before the container markup, but I wanted to keep the markup examples focused on a single card element rather than on the full grid, so I went with this version.

When the content has finished loading and is displayed in the DOM, we need to toggle aria-hidden to false for content containers and toggle aria-hidden to true on a visually hidden loading text indicator.

Here’s the finished example CodePen Embed Fallback That’s a wrap

Implementing skeleton loaders requires a slightly different approach than implementing regular loading elements, like spinners. I’ve seen numerous examples around the web that implement skeleton loaders in a way that severely limits their reusability. These over-engineered solutions usually involve creating separate skeleton loader UI components with dedicated (narrow-scope) skeleton CSS markup or recreating the layout with CSS gradients and magic numbers. We’ve seen that only the content needs to be replaced with the skeleton loaders, and not the entire component.

We’ve managed to create simple, versatile, and reusable skeleton loaders that inherit the layout from the default styles and replace the content inside the empty containers with solid boxes. With just two CSS classes, these skeleton loaders can easily be added to virtually any HTML element and extended, if needed. We’ve also made sure that this solution is accessible and doesn’t bloat the markup with additional HTML elements or duplicated UI components.

Thank you for taking the time to read this article. Let me know your thoughts on this approach and let me know how did you approach creating skeleton loaders in your projects.

The post A Bare-Bones Approach to Versatile and Reusable Skeleton Loaders appeared first on CSS-Tricks.

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React Without Build Tools

Css Tricks - Wed, 03/03/2021 - 3:42am

Jim Nielsen:

I think you’ll find it quite refreshing to use React A) with a JSX-like syntax, and B) without any kind of build tooling.

Refreshing indeed:

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It’s not really the React that’s the hard part to pull off without build tools (although I do wonder what we lose from not tree shaking), it’s the JSX. I’m so used to JSX I think it would be hard for me to work on a front-end JavaScript project without it. But I know some people literally prefer a render function instead. If that’s the case, you could use React.createComponent directly and skip the JSX, or in the case of Preact, use h:

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I work on a project that uses Mithril for the JavaScript templating which is a bit like that, and it’s not my favorite syntax, but you totally get used to it (and it’s fast):

CodePen Embed Fallback

Direct Link to ArticlePermalink

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How to Animate the Details Element

Css Tricks - Tue, 03/02/2021 - 10:58am

Here’s a nice simple demo from Moritz Gießmann on animating the triangle of a <details> element, which is the affordance that tells people this thing can be opened. Animating it, then is another kind of affordance that tells people this thing is opening now.

The tricks?

  1. Turn off the default triangle: details summary::-webkit-details-marker { display:none; }. You can’t animate that one.
  2. Make a replacement triangle with the CSS border trick and a pseudo element.
  3. Animate the new triangle when the state is open: details[open] > summary::before { transform: rotate(90deg); }.
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This only animates the triangle. The content inside still “snaps” open. Wanna smooth things out? Louis Hoebregts’ “How to Animate the Details Element Using WAAPI” covers that.

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Here’s a fork where I’ll combine them just because:

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I see Moritz put the cursor: pointer; on the summary as well like Greg Gibson suggests.

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The Best Font Loading Strategies and How to Execute Them

Css Tricks - Tue, 03/02/2021 - 6:00am

Zach Leatherman wrote up a comprehensive list of font loading strategies that have been widely shared in the web development field. I took a look at this list before, but got so scared (and confused), that I decided not to do anything at all. I don’t know how to begin loading fonts the best way and I don’t want to feel like an idiot going through this list.

Today, I gave myself time to sit down and figure it out. In this article, I want to share with you the best loading strategies and how to execute all of them.

The best strategies

Zach recommends two strategies in his article:

  1. FOUT with Class – Best approach for most situations. (This works whether we use a font-hosting company or hosting our own fonts.)
  2. Critical FOFT – Most performant approach. (This only works if we host our own fonts.)

Before we dive into these two strategies, we need to clear up the acronyms so you understand what Zach is saying.


The acronyms are as follows:

  • FOIT means flash of invisible text. When web fonts are loading, we hide text so users don’t see anything. We only show the text when web fonts are loaded.
  • FOUT means flash of unstyled text. When web fonts are loading, we show users a system font. When the web font gets loaded, we change the text back to the desired web font.
  • FOFT means flash of faux text. This one is complicated and warrants more explanation. We’ll talk about it in detail when we hit the FOFT section.
Self-hosted fonts vs. cloud-hosted fonts

There are two main ways to host fonts:

  1. Use a cloud provider.
  2. Self-host the fonts.

How we load fonts differs greatly depending on which option you choose.

Loading fonts with cloud-hosted fonts

It’s often easier to cloud-hosted fonts. The provider will give us a link to load the fonts. We can simply plunk this link into our HTML and we’ll get our web font. Here’s an example where we load web fonts from Adobe Fonts now (previously known as Typekit).

<link rel="stylesheet" href="https://use.typekit.net/your-kit-id.css">

Unfortunately, this isn’t the best approach. The href blocks the browser. If loading the web font hangs, users won’t be able to do anything while they wait.

Typekit used to provide JavaScript that loads a font asynchronously. It’s a pity they don’t show this JavaScript version anymore. (The code still works though, but I have no idea when, or if, it will stop working.)

Loading fonts from Google Fonts is slightly better because it provides font-display: swap. Here’s an example where we load Lato from Google Fonts. (The display=swap parameter triggers font-display: swap).

<link href="https://fonts.googleapis.com/css2?family=Lato:ital,wght@0,400;0,700;1,400;1,700&display=swap" rel="stylesheet" /> Loading fonts with self-hosted fonts

You can only self-host your fonts if you have the license to do so. Since fonts can be expensive, most people choose to use a cloud provider instead.

There’s a cheap way to get fonts though. Design Cuts runs font deals occasionally where you can get insanely high-quality fonts for just $29 per bundle. Each bundle can contain up to 12 fonts. I managed to get classics like Claredon, DIN, Futura, and a whole slew of fonts I can play around by camping on their newsletter for these deals.

If we want to self-host fonts, we need to understand two more concepts: @font-face and font-display: swap.


@font-face lets us declare fonts in CSS. If we want to self-host fonts, we need to use @font-face to declare your fonts.

In this declaration, we can specify four things:

  • font-family: This tells CSS (and JavaScript) the name of our font.
  • src: Path to find the font so they can get loaded
  • font-weight: The font weight. Defaults to 400 if omitted.
  • font-style: Whether to italicize the font. Defaults to normal if omitted.

For src, we need to specify several font formats. For a practical level of browser support, we can use woff2 and woff.

Here’s an example where we load Lato via @font-face.

@font-face { font-family: Lato; src: url('path-to-lato.woff2') format('woff2'), url('path-to-lato.woff') format('woff'); } @font-face { font-family: Lato; src: url('path-to-lato-bold.woff2') format('woff2'), url('path-to-lato-bold.woff') format('woff'); font-weight: 700; } @font-face { font-family: Lato; src: url('path-to-lato-italic.woff2') format('woff2'), url('path-to-lato-italic.woff') format('woff'); font-style: italic; } @font-face { font-family: Lato; src: url('path-to-lato-bold-italic.woff2') format('woff2'), url('path-to-lato-bold-italic.woff') format('woff'); font-weight: 700; font-style: italic; }

If you don’t have woff2 or woff files, you can upload your font files (either Opentype or Truetype) into a font-face generator to get them.

Next, we declare the web font in a font-family property.

html { font-family: Lato, sans-serif; }

When browsers parse an element with the web font, they trigger a download for the web font.

font-display: swap

font-display takes one of four possible values: auto, swap, fallback, and optional. swap instructs browsers to display the fallback text before web fonts get loaded. In other words, swap triggers FOUT for self-hosted fonts. Find out about other values from in the CSS-Tricks almanac.

Browser support for font-display: swap is pretty good nowadays so we can use it in our projects.

This browser support data is from Caniuse, which has more detail. A number indicates that browser supports the feature at that version and up.

DesktopChromeFirefoxIEEdgeSafari6058No7911.1Mobile / TabletAndroid ChromeAndroid FirefoxAndroidiOS Safari88868111.3-11.4 FOUT vs. FOUT with Class

FOUT means flash of unstyled text. You always want FOUT over FOIT (flash of invisible text) because it’s better for users to read words written with system fonts compared to words written with invisible ink. We mentioned earlier that font-display: swap gives you the ability to use FOUT natively.

FOUT with Class gives you the same results—FOUT—but it uses JavaScript to load the fonts. The mechanics are as follows:

  • First: Load system fonts.
  • Second: Load web fonts via JavaScript.
  • Third: When web fonts are loaded, add a class to the <html> tag.
  • Fourth: Switch the system font with the loaded web font.

Zach recommends loading fonts via JavaScript even though font-display: swap enjoys good browser support. In other words, Zach recommends FOUT with Class over @font-face + font-display: swap.

He recommends FOUT with Class because of these three reasons:

  1. We can group repaints.
  2. We can adapt to user preferences.
  3. We can skip font-loading altogether if users have a slow connection.

I’ll let you dive deeper into the reasons in another article. While writing this article, I found a fourth reason to prefer FOUT with Class: We can skip font-loading when users already have the font loaded in their system. (We do this with sessionStorage as we’ll see below.)

FOUT with Class (for cloud-hosted fonts)

First, we want to load our fonts as usual from your cloud-hosting company. Here’s an example where I loaded Lato from Google Fonts:

<head> <link href="https://fonts.googleapis.com/css2?family=Lato:ital,wght@0,400;0,700;1,400;1,700&display=swap" rel="stylesheet" /> </head>

Next, we want to load fonts via JavaScript. We’ll inject a script into the <head> section since the code footprint is small, and it’s going to be asynchronous anyway.

<head> <link href="https://fonts.googleapis.com/css2?family=Lato:ital,wght@0,400;0,700;1,400;1,700&display=swap" rel="stylesheet" /> <script src="js/load-fonts.js"></script> </head>

In load-fonts.js, we want to use the CSS Font Loading API to load the font. Here, we can use Promise.all to load all fonts simultaneously. When we do this, we’re grouping repaints.

The code looks like this:

if ('fonts' in document) { Promise.all([ document.fonts.load('1em Lato'), document.fonts.load('700 1em Lato'), document.fonts.load('italic 1em Lato'), document.fonts.load('italic 700 1em Lato') ]).then(_ => () { document.documentElement.classList.add('fonts-loaded') }) }

When fonts are loaded, we want to change the body text to the web font. We can do this via CSS by using the .fonts-loaded class.

/* System font before [[webfont]]s get loaded */ body { font-family: sans-serif; } /* Use [[webfont]] when [[webfont]] gets loaded*/ .fonts-loaded body { font-family: Lato, sans-serif; }

Pay attention here: We need to use the .fonts-loaded class with this approach.

We cannot write the web font directly in the <body>‘s font-family; doing this will trigger fonts to download, which means you’re using @font-face + font-display: swap. It also means the JavaScript is redundant.

/* DO NOT DO THIS */ body { font-family: Lato, sans-serif; }

If users visit additional pages on the site, they already have the fonts loaded in their browser. We can skip the font-loading process (to speed things up) by using sessionStorage.

if (sessionStorage.fontsLoaded) { document.documentElement.classList.add('fonts-loaded') } else { if ('fonts' in document) { Promise.all([ document.fonts.load('1em Lato'), document.fonts.load('700 1em Lato'), document.fonts.load('italic 1em Lato'), document.fonts.load('italic 700 1em Lato') ]).then(_ => () { document.documentElement.classList.add('fonts-loaded') }) } }

If we want to optimize the JavaScript for readability, we can use an early return pattern to reduce indentation.

function loadFonts () { if (sessionStorage.fontsLoaded) { document.documentElement.classList.add('fonts-loaded') return } if ('fonts' in document) { Promise.all([ document.fonts.load('1em Lato'), document.fonts.load('700 1em Lato'), document.fonts.load('italic 1em Lato'), document.fonts.load('italic 700 1em Lato') ]).then(_ => () { document.documentElement.classList.add('fonts-loaded') }) } loadFonts() FOUT with Class (for self-hosted fonts)

First, we want to load our fonts as usual via @font-face. The font-display: swap property is optional since we’re loading fonts via JavaScript.

@font-face { font-family: Lato; src: url('path-to-lato.woff2') format('woff2'), url('path-to-lato.woff') format('woff'); } /* Other @font-face declarations */

Next, we load the web fonts via JavaScript.

if ('fonts' in document) { Promise.all([ document.fonts.load('1em Lato'), document.fonts.load('700 1em Lato'), document.fonts.load('italic 1em Lato'), document.fonts.load('italic 700 1em Lato') ]).then(_ => () { document.documentElement.classList.add('fonts-loaded') }) }

Then we want to change the body text to the web font via CSS:

/* System font before webfont is loaded */ body { font-family: sans-serif; } /* Use webfont when it loads */ .fonts-loaded body { font-family: Lato, sans-serif; }

Finally, we skip font loading for repeat visits.

if ('fonts' in document) { Promise.all([ document.fonts.load('1em Lato'), document.fonts.load('700 1em Lato'), document.fonts.load('italic 1em Lato'), document.fonts.load('italic 700 1em Lato') ]).then(_ => () { document.documentElement.classList.add('fonts-loaded') }) } CSS Font Loader API vs. FontFaceObserver

The CSS Font Loader API has pretty good browser support, but it’s a pretty cranky API.

This browser support data is from Caniuse, which has more detail. A number indicates that browser supports the feature at that version and up.

DesktopChromeFirefoxIEEdgeSafari3541No7910Mobile / TabletAndroid ChromeAndroid FirefoxAndroidiOS Safari88868110.0-10.2

So, if you need to support older browsers (like IE 11 and below), or if you find the API weird and unwieldy, you might want to use Bramstein’s FontFaceObserver. It’s super lightweight so there’s not much harm.

The code looks like this. (It’s much nicer compared to the CSS Font Loader API).

new FontFaceObserver('lato') .load() .then(_ => { document.documentElement.classList.add('fonts-loaded') })

Make sure to use fontfaceobserver.standalone.js if you intend to it to load fonts on browsers that don’t support Promises.


FOFT means flash of faux text. The idea here is we split font loading into three stages:

  • Step 1: Use fallback font when web fonts aren’t loaded yet.
  • Step 2: Load the Roman (also called “book” or “regular”) version of the font first. This replaces most of the text. Bold and italics will be faked by the browser (hence “faux text”).
  • Step 3: Load the rest of the fonts

Note: Zach also calls this Standard FOFT.

Using Standard FOFT

First, we load the Roman font.

@font-face { font-family: LatoInitial; src: url('path-to-lato.woff2') format('woff2'), url('path-to-lato.woff') format('woff'); unicode-range: U+65-90, U+97-122; } .fonts-loaded-1 body { font-family: LatoInitial; } if('fonts' in document) { document.fonts.load("1em LatoInitial") .then(_ => { document.documentElement.classList.add('fonts-loaded-1') }) }

Then, we load other fonts.

Pay attention here: we’re loading Lato again, but this time, we set font-family to Lato instead of LatoInitial.

/* Load this first */ @font-face { font-family: LatoInitial; src: url('path-to-lato.woff2') format('woff2'), url('path-to-lato.woff') format('woff'); unicode-range: U+65-90, U+97-122; } /* Load these afterwards */ @font-face { font-family: Lato; src: url('path-to-lato.woff2') format('woff2'), url('path-to-lato.woff') format('woff'); unicode-range: U+65-90, U+97-122; } /* Other @font-face for different weights and styles*/ .fonts-loaded-1 body { font-family: LatoInitial; } .fonts-loaded-2 body { font-family: Lato; } if ('fonts' in document) { document.fonts.load('1em LatoInitial') .then(_ => { document.documentElement.classList.add('fonts-loaded-1') Promise.all([ document.fonts.load('400 1em Lato'), document.fonts.load('700 1em Lato'), document.fonts.load('italic 1em Lato'), document.fonts.load('italic 700 1em Lato') ]).then(_ => { document.documentElement.classList.add('fonts-loaded-2') }) }) }

Again, we can optimize it for repeat views.

Here, we can add fonts-loaded-2 to the <html> straightaway since fonts are already loaded.

function loadFonts () { if (sessionStorage.fontsLoaded) { document.documentElement.classList.add('fonts-loaded-2') return } if ('fonts' in document) { document.fonts.load('1em Lato') .then(_ => { document.documentElement.classList.add('fonts-loaded-1') Promise.all([ document.fonts.load('400 1em Lato'), document.fonts.load('700 1em Lato'), document.fonts.load('italic 1em Lato'), document.fonts.load('italic 700 1em Lato') ]).then(_ => { document.documentElement.classList.add('fonts-loaded-2') // Optimization for Repeat Views sessionStorage.fontsLoaded = true }) }) } } Critical FOFT

The “critical” part comes from ‘critical css” (I believe) – where we load only essential CSS before loading the rest. We do this because it improves performance.
When it comes to typography, the only critical things are letters A to Z (both capitals and small letters). We can create a subset of these fonts with unicode-range.

When we create this subset, we can also create a separate font file with the necessary characters.

Here’s what @font-face declaration looks like:

@font-face { font-family: LatoSubset; src: url('path-to-optimized-lato.woff2') format('woff2'), url('path-to-optimized-lato.woff') format('woff'); unicode-range: U+65-90, U+97-122; }

We load this subset first.

.fonts-loaded-1 body { font-family: LatoSubset; } if('fonts' in document) { document.fonts.load('1em LatoSubset') .then(_ => { document.documentElement.classList.add('fonts-loaded-1') }) }

And we load other font files later.

.fonts-loaded-2 body { font-family: Lato; } if ('fonts' in document) { document.fonts.load('1em LatoSubset') .then(_ => { document.documentElement.classList.add('fonts-loaded-1') Promise.all([ document.fonts.load('400 1em Lato'), document.fonts.load('700 1em Lato'), document.fonts.load('italic 1em Lato'), document.fonts.load('italic 700 1em Lato') ]).then(_ => { document.documentElement.classList.add('fonts-loaded-2') }) }) }

Again, we can optimize it for repeat views:

function loadFonts () { if (sessionStorage.fontsLoaded) { document.documentElement.classList.add('fonts-loaded-2') return } if ('fonts' in document) { document.fonts.load('1em LatoSubset') .then(_ => { document.documentElement.classList.add('fonts-loaded-1') Promise.all([ document.fonts.load('400 1em Lato'), document.fonts.load('700 1em Lato'), document.fonts.load('italic 1em Lato'), document.fonts.load('italic 700 1em Lato') ]).then(_ => { document.documentElement.classList.add('fonts-loaded-2') // Optimization for Repeat Views sessionStorage.fontsLoaded = true }) }) } } Critical FOFT variants

Zach proposed two additional Critical FOFT variants:

  • Critical FOFT with Data URI
  • Critical FOFT with Preload
Critical FOFT with data URIs

In this variant, we load the critical font (the subsetted roman font) with data URIs instead of a normal link. Here’s what it looks like. (And it’s scary.)

@font-face { font-family: LatoSubset; src: url("data:application/x-font-woff;charset=utf-8;base64,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") format("woff"); /* ... */ }

This code looks scary, but there’s no need to be scared. The hardest part here is generating the data URI, and CSS-Tricks has us covered here.

Critical FOFT with preload

In this variant, we add a link with the preload tag to the critical font file. Here’s what it looks like:

<link rel="preload" href="path-to-roman-subset.woff2" as="font" type="font/woff2" crossorigin>

We should only preload one font here. If we load more than one, we can adversely affect the initial load time.

In the strategy list, Zach also mentioned he prefers using a data URI over the preload variant. He only prefers it because browser support for preload used to be bad. Today, I feel that browser support is decent enough to choose preloading over a data URI.

This browser support data is from Caniuse, which has more detail. A number indicates that browser supports the feature at that version and up.

DesktopChromeFirefoxIEEdgeSafari5085No7911.1Mobile / TabletAndroid ChromeAndroid FirefoxAndroidiOS Safari88868111.3-11.4 Final note from Zach

Chris ran this article via Zach and Zach wished he prioritized a JavaScript-free approach in his original article.

I think the article is good but I think my article that its based off of is probably a little dated in a few ways. I wish it prioritized no-JS approaches more when you’re only using one or two font files (or more but only 1 or 2 of each typeface). The JS approaches are kind of the exception nowadays I think (unless you’re using a lot of font files or a cloud provider that doesn’t support font-display: swap)

This switches the verdict a tiny bit, which I’m going to summarize in the next section.

Which font loading strategy to use?

If you use a cloud-hosted provider:

  • Use font-display: swap if the host provides it.
  • Otherwise, use FOUT with class

If you host your web fonts, you have a few choices:

  1. @font-face + font-display: swap
  2. FOUT with Class
  3. Standard FOFT
  4. Critical FOFT

Here’s how to choose between them:

  • Choose @font-face + font-display: swap if you’re starting out and don’t want to mess with JavaScript. It’s the simplest of them all. Also choose this option if you use only few font files (fewer than two files) for each typeface.
  • Choose Standard FOFT if you’re ready to use JavaScript, but don’t want to do the extra work of subsetting the Roman font.
  • Choose a Critical FOFT variant if you want to go all the way for performance.

That’s it! I hope you found all of this useful!

If you loved this article, you may like other articles I wrote. Consider subscribing to my newsletter &#x1f609;. Also, feel free to reach out to me if you have questions. I’ll try my best to help!

The post The Best Font Loading Strategies and How to Execute Them appeared first on CSS-Tricks.

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The “Gray Dead Zone” of Gradients

Css Tricks - Mon, 03/01/2021 - 9:16am

Erik D. Kennedy notes an interesting phenomenon of color gradients. If you have a gradient between two colors where the line between them in the color space goes through the zero-saturation middle, you get this “gray dead zone” in the middle.

It’s a real thing. See the gray middle here:

CodePen Embed Fallback

You can also see how colors might not do that, like red and blue here shooting right through purple instead, which you can visualize on that color circle above.

CodePen Embed Fallback

Erik says one solution can be taking a little detour instead of going straight through the gray zone:

His updated gradient tool deals with this by using different “interpolation modes” and easing the gradient with a choice of precision stops. Don’t miss the radial and conic options as well, with the ability to place the centers “offscreen” which can yield pretty cool looks you can’t do any other way.

Oh and speaking of conic gradients, Adam Argyle has a little gallery of possibilities that is pretty unique.

The post The “Gray Dead Zone” of Gradients appeared first on CSS-Tricks.

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How to Map Mouse Position in CSS

Css Tricks - Mon, 03/01/2021 - 5:45am

Let’s look at how to get the user’s mouse position and map it into CSS custom properties: --positionX and --positionY.

We could do this in JavaScript. If we did, we could do things like make make an element draggable or move a background. But actually, we can still do similar things, but not use any JavaScript!

I’ve used this method as a part of a demo I’ve made for getting a ‘Click and drag’ effect with pure CSS. I used the perspective tips from my pervious article. It’s a pretty neat effect to get this done entirely in CSS, which might have wider usefulness than my demo, so let’s take a look.

The setup

Our first demo is going to use --positionX and --positionY custom properties to set the width and height of an element.

CodePen Embed Fallback

Heads up that we’re only using SCSS here for brevity, but all of this can be done in pure CSS.

This is our initial state. We have here a ‘wrapper’ <div> with a .content class of that is spread to the width and height of the body. This <div> will host the content of our project, and the elements we want to control using the mouse position – in this case, the .square element.

We’ve also added the two custom-properties to the content. we will use the mouse position to set the value of these properties, and then use them set the .square element’s width and height accordingly.

Once we have mapped the custom properties for mouse position, we can use them to do pretty much anything we want . For example, we could use them to set the top / left properties of an absolute positioned element, control a transform property, set the background-position, manipulate colors, or even set the content of a pseudo-element. We’ll see some of these bonus demos at the end of the article.

The grid

The goal is to create an invisible grid on the screen, and use the :hover pseudo-class to map each ‘cell’ to a set of values that we will allocate to the custom properties. So, when the mouse cursor moves to the right side of the screen, the value of the --positionX will be higher; and when it moves to left, it gets lower. We’ll do the same with --positionY: the value will be lower as the cursor moves to the top, and higher when it moves to the bottom.

A few words about the grid size we’re using: We can actually make the grid whatever size we want. The larger it is, the more accurate our custom property values will be. But that also means we will have more cells, which can lead to performance issues. It’s important to maintain proper balance and adjust the grid size to the specific needs of each project.

For now, lets say that we want a 10×10 grid for a total of 100 cells in our markup. (And yes, it’s OK to use Pug for that, even though I won’t in this example.)

<div class="cell"></div> <div class="cell"></div> <div class="cell"></div> <!-- 97 more cells --> <div class="content"> <div class="square"></div> </div>

You’re probably wondering why the .cell elements come before the .content. That’s because of the cascade.

We want to use the .cell class to control the .square, and the way the cascade works (for now) is that an element can only control its children (or descendants) and its siblings (or their descendants) — but only as long as the sibling is after the controlling element.

That means two things:

  1. Each .cell must come before the element we want to control (in this case, the .square).
  2. We can’t put those .cells in a container, because if we do, the .content is no longer their sibling.
Positioning the cells

There are a few ways to position the .cells. we can position: absolute them and offset them with the top and left properties. Or we can translate them into position using transform. But the easiest option is likely using display: grid.

body { background-color: #000; height: 100vh; display: grid; grid-template: repeat(10, 1fr) / repeat(10, 1fr); } .cell { width: 100%; height: 100%; border: 1px solid gray; z-index: 2; }
  • The border is just temporary, so we could see the cells on the screen. we’ll remove it later on.
  • the z-index is important, because we want the cells to be in front of the content.

Here’s what we have so far:

CodePen Embed Fallback Adding values

We want to use .cell to set the --positionX and --positionY values.

When we hover over a .cell that is in the first (left) column, the value of --positionX should be 0. When we hover over a .cell in the second column, the value should be 1. It should be 2 in the third column, and so on.

The same goes for the y-axis. When we hover over a .cell that is in the first (top) row, --positionY should be 0, and when we hover over a cell in the second row, the value should be 1, and so on.

The numbers in this image represent the numbers of the cell elements in the grid. If we take just a single .cell as an example — let’s say cell 42 — we can select it using :nth-child():

.cell:nth-child(42) { }

But we need to remember a couple of things:

  1. We only want this selector to work when we hover over the cell, so we will attach :hover to it.
  2. We want to select the .content instead of the cell itself, so we’ll use the General Sibling Combinator (~) to do that.

So now, to set --positionX to 1 and --positionY to 3 for .content when the 42nd cell is hovered, we need to do something like this:

.cell:nth-child(42):hover ~ .content { --positionX: 1; --positionY: 3; }

But who wants to do that 100 times!? There are a few approaches to make things easier:

  1. Use a Sass @for loop to go through all 100 cells, and do some math to set the proper --positionX and --positionY values for each iteration.
  2. Separate the x- and y-axes to select each row and each column individually with :nth-child’s functional notation.
  3. Combine those two approaches and use a Sass @for loop and :nth-child functional notation.

I thought long and hard about what would be the best and easiest approach to take, and while all of then have pros and cons, I landed on the third approach. The amount of code to write, the quality of the compiled code, and the math complexity all went into my thinking. Don’t agree? Tell my why in the comments!

Setting values with a @for loop @for $i from 0 to 10 { .cell:nth-child(???):hover ~ .content { --positionX: #{$i}; } .cell:nth-child(???):hover ~ .content { --positionY: #{$i}; } }

This is the basic loop. We’re going over it 10 times since we have 10 rows and 10 columns. And we’ve separated the x- and y-axes to set --positionX for each column, and the --positionY for each row. All we need to do now is to replace those ??? things with the proper notation to select each row and column.

Let’s start with the x-axis

Going back to our grid image (the one with numbers),We can see that the numbers of all the cells in the second column are multiples of 10, plus 2. The cells in the third column are multiples of 10 plus 3. And so on.

Now let’s ‘translate’ it into the :nth-child functional notation. Here’s how that looks for the second column:

:nth-child(10n + 2)
  • 10n selects every multiple of 10.
  • 2 is the column number.

And for our loop, we will replace the column number with #{$i + 1} to iterate sequentially:

.cell:nth-child(10n + #{$i + 1}):hover ~ .content { --positionX: #{$i}; } Now lets deal with the y-axis

Look again at the grid image and focus on the fourth row. The cell numbers are somewhere between 41 and 50. The cells in the fifth row are between 51 to 60, and so on. To select each row, we’ll need to define its range. For example, the range for the fourth row is:

.cell:nth-child(n + 41):nth-child(-n + 50)
  • (n + 41) is the start of the range.
  • (-n + 50) is the end of the range.

Now we’ll replace the numbers with some math on the $i value. For the start of the range, we get (n + #{10 * $i + 1}), and for the end of the range we get (-n + #{10 * ($i + 1)}).

So the final @for loop is:

@for $i from 0 to 10 { .cell:nth-child(10n + #{$i + 1}):hover ~ .content { --positionX: #{$i}; } .cell:nth-child(n + #{10 * $i + 1}):nth-child(-n + #{10 * ($i + 1)}):hover ~ .content { --positionY: #{$i}; } }

The mapping is done! When we hover over elements, --positionX and --positionY change according to the mouse position. That means we can use them to control the elements inside the .content.

Handling the custom properties

OK, so now we have the mouse position mapped to two custom-properties, The next thing is to use them to control the .square element’s width and height values.

Let’s start with the width and say that we want the minimum width of the .square to be 100px (i.e. when the mouse cursor is at the left side of the screen), and we want it to grow 20px for each step the mouse cursor moves to the right.

Using calc(), we can do that:

.square { width: calc(100px + var(--positionX) * 20px); }

And of course, we’ll do the same for the height, but with --positionY instead:

.square { width: calc(100px + var(--positionX) * 20px); height: calc(100px + var(--positionY) * 20px); }

That’s it! Now we have a simple .square element, with a width and height that is controlled by the mouse position. Move your mouse cursor over the window, and see how the square changes its width and height accordingly.

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I added a small transition to make the effect smoother. That’s not required, of course. And I’ve also commented out on the .cell border.

Let’s try an alternative method

There might be a case where you want to ‘bypass’ --positionX and --positionY, and set the end value directly inside the @for loop. So, for our example it would look like this:

@for $i from 0 to 10 { .cell:nth-child(10n + #{$i + 1}):hover ~ .content { --squareWidth: #{100 + $i * 20}px; } .cell:nth-child(n + #{10 * $i + 1}):nth-child(-n + #{10 * ($i + 1)}):hover ~ .content { --squareHeight: #{100 + $i * 20}px;: #{$i}; } }

Then the .square would use the custom properties like this:

.square { width: var(--squareWidth); height: var(--squareHeight); }

This method is a little more flexible because it allows for more advanced Sass math (and string) functions. That said, the general principle is absolutely the same as what we already covered.

What’s next?

Well, the rest is up to you — and the possibilities are endless! How do you think you’d use it? Can you take it further? Try using this trick in your CSS, and share your work in the comments or let me know about it on Twitter. It will be great to see a collection of these come together.

Here are a few examples to get your hamster wheel turning:

CodePen Embed Fallback CodePen Embed Fallback CodePen Embed Fallback CodePen Embed Fallback

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CSS Border Font

Css Tricks - Sun, 02/28/2021 - 6:11am

Every letter in this “font” by Davor Suljic is a single div and drawn only with border. That means employing some trickery like border-radius with exotic syntax like border-radius: 100% 100% 0 0 / 37.5% 37.5% 0 0; which rounds just the top of an element with a certain chillness that works here. Plus, using pseudo-elements. I love all the wacky variations with colors, shadows, and border styles, leaning into the limits of CSS.

Drawing things with CSS has long fascinated people. Icons are a popular choice (famously, Nicolas Gallagher’s Pure CSS GUI icons from 2010), since we can draw so many shapes with CSS without even needing to lean on the all-powerful clip-path.

But as Lynn Fisher has taught us, a single div is barely a limitation at all.

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Next.js on Netlify

Css Tricks - Sun, 02/28/2021 - 6:11am

(This is a sponsored post.)

If you want to put Next.js on Netlify, here’s a 5 minute tutorial¹. One of the many strengths of Next.js is that it can do server-side rendering (SSR) with a Node server behind it. But Netlify does static hosting not Node hosting, right? Well Netlify has functions, and those functions can handle the SSR. But you don’t even really need to know that, you can just use the plugin.

Need a little bit more hand-holding than that? You got it, Cassidy is doing a free Webinar about all the next Thursday (March 4th, 2021) at 9am Pacific. That way you can watch live and ask questions and stuff. Netlify has a bunch of webinars they have now smartly archived on a new resources site.

  1. I’ve also mentioned this before if it sounds familiar, the fact that it supports the best of the entire rendering spectrum is very good.

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Weekly Platform News: Reduced Motion, CORS, WhiteHouse.gov, popups, and 100vw

Css Tricks - Fri, 02/26/2021 - 7:00am

In this week’s roundup, we highlight a proposal for a new <popup> element, check the use of prefers-reduced-motion on award-winning sites, learn how to opt into cross-origin isolation, see how WhiteHouse.gov approaches accessibility, and warn the dangers of 100vh.

Let’s get into the news!

The new HTML <popup> element is in development

On January 21, Melanie Richards from the Microsoft Edge web platform team posted an explainer for a proposed HTML <popup> element (the name is not final). A few hours later, Mason Freed from Google announced an intent to prototype this element in the Blink browser engine. Work on the implementation is taking place in Chromium issue #1168738.

A popup is a temporary (transient) and “light-dismissable” UI element that is displayed on the the “top layer” of all other elements. The goal for the <popup> element is to be fully stylable and accessible by default. A <popup> can be anchored to an activating element, such as a button, but it can also be a standalone element that is displayed on page load (e.g., a teaching UI).

A <popup> is automatically hidden when the user presses the Esc key or moves focus to a different element (this is called a light dismissal). Unlike the <dialog> element, only one <popup> can be shown at a time, and unlike the deprecated <menu> element, a <popup> can contain arbitrary content, including interactive elements:

We imagine <popup> as being useful for various different types of popover UI. We’ve chosen to use an action menu as a primary example, but folks use popup-esque patterns for many different types of content.

Award-winning websites should honor the “reduce motion” preference

Earlier this week, AWWWARDS announced the winners of their annual awards for the best websites of 2020. The following websites were awarded:

All these websites are highly dynamic and show full-screen motion on load and during scroll. Unfortunately, such animations can cause dizziness and nausea in people with vestibular disorders. Websites are therefore advised to reduce or turn off non-essential animations via the prefers-reduced-motion media query, which evaluates to true for people who have expressed their preference for reduced motion (e.g., the “Reduce motion” option on Apple’s platforms). None of the winning websites do this.

/* (code from animal-crossing.com) */ @media (prefers-reduced-motion: reduce) { .main-header__scene { animation: none; } }

An example of a website that does this correctly is the official site of last year’s Animal Crossing game. Not only does the website honor the user’s preference via prefers-reduced-motion, but it also provides its own “Reduce motion” toggle button at the very top of the page.

(via Eric Bailey)

Websites can now opt into cross-origin isolation

Cross-origin isolation is part of a “long-term security improvement.” Websites can opt into cross-origin isolation by adding the following two HTTP response headers, which are already supported in Chrome and Firefox:

Cross-Origin-Embedder-Policy: require-corp Cross-Origin-Opener-Policy: same-origin

A cross-origin-isolated page relinquishes its ability to load content from other origins without their explicit opt-in (via CORS headers), and in return, the page gains access to some powerful APIs, such as SharedArrayBuffer.

if (crossOriginIsolated) { // post SharedArrayBuffer } else { // do something else } The White House recommits to accessibility

The new WhiteHouse.gov website of the Biden administration was built from scratch in just six weeks with accessibility as a top priority (“accessibility was top of mind”). Microsoft’s chief accessibility officer reviewed the site and gave it the thumbs up.

The website’s accessibility statement (linked from the site’s footer) declares a “commitment to accessibility” and directly references the latest version of the Web Content Accessibility Guidelines, WCAG 2.1 (2018). This is notable because federal agencies in the USA are only required to comply with WCAG 2.0 (2008).

The Web Content Accessibility Guidelines are the most widely accepted standards for internet accessibility. … By referencing WCAG 2.1 (the latest version of the guidelines), the Biden administration may be indicating a broader acceptance of the WCAG model.

The CSS 100vw value can cause a useless horizontal scrollbar

On Windows, when a web page has a vertical scrollbar, that scrollbar consumes space and reduces the width of the page’s <html> element; this is called a classic scrollbar. The same is not the case on macOS, which uses overlay scrollbars instead of classic scrollbars; a vertical overlay scrollbar does not affect the width of the <html> element.

macOS users can switch from overlay scrollbars to classic scrollbars by setting “Show scroll bars” to ”Always” in System preferences > General.

The CSS length value 100vw is equal to the width of the <html> element. However, if a classic vertical scrollbar is added to the page, the <html> element becomes narrower (as explained above), but 100vw stays the same. In other words, 100vw is wider than the page when a classic vertical scrollbar is present.

This can be a problem for web developers on macOS who use 100vw but are unaware of its peculiarity. For example, a website might set width: 100vw on its article header to make it full-width, but this will cause a useless horizontal scrollbar on Windows that some of the site’s visitors may find annoying.

Web developers on macOS can switch to classic scrollbars to make sure that overflow bugs caused by 100vw don’t slip under their radar. In the meantime, I have asked the CSS Working Group for comment.

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An Interactive Guide to CSS Transitions

Css Tricks - Thu, 02/25/2021 - 1:30pm

A wonderful post by Josh that both introduces CSS transitions and covers the nuances for using them effectively. I like the advice about transitioning the position of an element, leaving the original space it occupied alone so it doesn’t result in what he calls “doom flicker.” Six hundred and fifty years ago I created CSS Jitter Man to attempt to explain that idea.

The interactive stuff is really neat and helps explain the concepts. I’m a little jealous that Josh writes in MDX — meaning he’s got Markdown and JSX at his disposal. That means these demos can be little one-off React components. Here’s a thread that Josh did showing off how valuable that can be.

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