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Let’s spin up a basic Svelte site and integrate Tailwind into it for styling. One advantage of working with Tailwind is that there isn’t any context switching going back and forth between HTML and CSS, since you’re applying styles as classes right on the HTML. It’s all the in same file in Svelte anyway, but still, this way you don’t even need a <style> section in your .svelte files.

If you are a Svelte developer or enthusiast, and you’d like to use Tailwind CSS in your Svelte app, this article looks at the easiest, most-straightforward way to install tailwind in your app and hit the ground running in creating a unique, modern UI for your app.

If you like to just see a working example, here’s a working GitHub repo.

Step 1: Scaffold a new Svelte site

Svelte provides us with a starter template we can use. You can get it by either cloning the Svelte GitHub repo, or by using degit. Using degit provides us with certain advantages, like helping us make a copy of the starter template repository without downloading its entire Git history (unlike git clone). This makes the process faster. Note that degit requires Node 8 and above.

Run the following command to clone the starter app template with degit:

npx degit sveltejs/template project-name

Navigate into the directory of the starter project so we can start making changes to it:

cd project-name

The template is mostly empty right now, so we’ll need to install some required npm packages:

npm install

Now that you have your Svelte app ready, you can proceed to combining it with Tailwind CSS to create a fast, light, unique web app.

Step 2: Adding Tailwind CSS

Let’s proceed to adding Tailwind CSS to our Svelte app, along with some dev dependencies that will help with its setup.

npm install tailwindcss@npm:@tailwindcss/postcss7-compat postcss@^7 autoprefixer@^9 # or yarn add tailwindcss@npm:@tailwindcss/postcss7-compat postcss@^7 autoprefixer@^9

The three tools we are downloading with the command above:

1. Tailwind
2. PostCSS
3. Autoprefixer

PostCSS is a tool that uses JavaScript to transform and improve CSS. It comes with a bunch of plugins that perform different functions like polyfilling future CSS features, highlighting errors in your CSS code, controlling the scope of CSS class names, etc.

Autoprefixer is a PostCSS plugin that goes through your code adding vendor prefixes to your CSS rules (Tailwind does not do this automatically), using caniuse as reference. While browsers are choosing to not use prefixing on CSS properties the way they had in years past, some older browsers still rely on them. Autoprefixer helps with that backwards compatibility, while also supporting future compatibility for browsers that might apply a prefix to a property prior to it becoming a standard.

For now, Svelte works with an older version of PostCSS. Its latest version, PostCSS 8, was released September 2020. So, to avoid getting any version-related errors, our command above specifies PostCSS 7 instead of 8. A PostCSS 7 compatibility build of Tailwind is made available under the compat channel on npm.

Step 3: Configuring Tailwind

Now that we have Tailwind installed, let’s create the configuration file needed and do the necessary setup. In the root directory of your project, run this to create a tailwind.config.js file:

npx tailwindcss init tailwind.config.js

Being a highly customizable framework, Tailwind allows us to easily override its default configurations with custom configurations inside this tailwind.config.js file. This is where we can easily customize things like spacing, colors, fonts, etc.

The tailwind.config.js file is provided to prevent ‘fighting the framework’ which is common with other CSS libraries. Rather than struggling to reverse the effect of certain classes, you come here and specify what you want. It’s in this file that we also define the PostCSS plugins used in the project.

The file comes with some default code. Open it in your text editor and add this compatibility code to it:

future: { purgeLayersByDefault: true, removeDeprecatedGapUtilities: true,
},

Tailwind 2.0 (the latest version), all layers (e.g., base, components, and utilities) are purged by default. In previous versions, however, just the utilities layer is purged. We can manually configure Tailwind to purge all layers by setting the purgeLayersByDefault flag to true.

Tailwind 2.0 also removes some gap utilities, replacing them with new ones. We can manually remove them from our code by setting removeDeprecatedGapUtilities to true.

These will help you handle deprecations and breaking changes from future updates.

PurgeCSS

The several thousand utility classes that come with Tailwind are added to your project by default. So, even if you don’t use a single Tailwind class in your HTML, your project still carries the entire library, making it rather bulky. We’ll want our files to be as small as possible in production, so we can use purge to remove all of the unused utility classes from our project before pushing the code to production.

Since this is mainly a production problem, we specify that purge should only be enabled in production.

purge: { content: [ "./src/**/*.svelte", ], enabled: production // disable purge in dev
},

Now, your tailwind.config.js should look like this:

const production = !process.env.ROLLUP_WATCH;
module.exports = { future: { purgeLayersByDefault: true, removeDeprecatedGapUtilities: true, }, plugins: [ ], purge: { content: [ "./src/**/*.svelte", ], enabled: production // disable purge in dev },
};

Rollup.js

Our Svelte app uses Rollup.js, a JavaScript module bundler made by Rich Harris, the creator of Svelte, that is used for compiling multiple source files into one single bundle (similar to webpack). In our app, Rollup performs its function inside a configuration file called rollup.config.js.

With Rollup, We can freely break our project up into small, individual files to make development easier. Rollup also helps to lint, prettify, and syntax-check our source code during bundling.

Step 4: Making Tailwind compatible with Svelte

Navigate to rollup.config.js and import the sveltePreprocess package. This package helps us handle all the CSS processing required with PostCSS and Tailwind.

import sveltePreprocess from "svelte-preprocess";

Under plugins, add sveltePreprocess and require Tailwind and Autoprefixer, as Autoprefixer will be processing the CSS generated by these tools.

preprocess: sveltePreprocess({ sourceMap: !production, postcss: { plugins: [ require("tailwindcss"), require("autoprefixer"), ], },
}),

Since PostCSS is an external tool with a syntax that’s different from Svelte’s framework, we need a preprocessor to process it and make it compatible with our Svelte code. That’s where the sveltePreprocess package comes in. It provides support for PostCSS and its plugins. We specify to the sveltePreprocess package that we are going to require two external plugins from PostCSS, Tailwind and Autoprefixer. sveltePreprocess runs the foreign code from these two plugins through Babel and converts them to code supported by the Svelte compiler (ES6+). Rollup eventually bundles all of the code together.

The next step is to inject Tailwind’s styles into our app using the @tailwind directive. You can think of @tailwind loosely as a function that helps import and access the files containing Tailwind’s styles. We need to import three sets of styles.

The first set of styles is @tailwind base. This injects Tailwind’s base styles—mostly pulled straight from Normalize.css—into our CSS. Think of the styles you commonly see at the top of stylesheets. Tailwind calls these Preflight styles. They are provided to help solve cross-browser inconsistencies. In other words, they remove all the styles that come with different browsers, ensuring that only the styles you employ are rendered. Preflight helps remove default margins, make headings and lists unstyled by default, and a host of other things. Here’s a complete reference of all the Preflight styles.

The second set of styles is @tailwind components. While Tailwind is a utility-first library created to prevent generic designs, it’s almost impossible to not reuse some designs (or components) when working on a large project. Think about it. The fact that you want a unique-looking website doesn’t mean that all the buttons on a page should be designed differently from each other. You’ll likely use a button style throughout the app.

Follow this thought process. We avoid frameworks, like Bootstrap, to prevent using the same kind of button that everyone else uses. Instead, we use Tailwind to create our own unique button. Great! But we might want to use this nice-looking button we just created on different pages. In this case, it should become a component. Same goes for forms, cards, badges etc.

All the components you create will eventually be injected into the position that @tailwind components occupies. Unlike other frameworks, Tailwind doesn’t come with lots of predefined components, but there are a few. If you aren’t creating components and plan to only use the utility styles, then there’s no need to add this directive.

And, lastly, there’s @tailwind utilities. Tailwind’s utility classes are injected here, along with the ones you create.

Step 5: Injecting Tailwind Styles into Your Site

It’s best to inject all of the above into a high-level component so they’re accessible on every page. You can inject them in the App.svelte file:

<style global lang="postcss"> @tailwind base; @tailwind components; @tailwind utilities;
</style>

Now that we have Tailwind set up in, let’s create a website header to see how tailwind works with Svelte. We’ll create it in App.svelte, inside the main tag.

Step 6: Creating A Website Header

Starting with some basic markup:

<nav> <div> <div> <a href="#">APP LOGO</a> <!-- Menus --> <div> <ul> <li> <a href="#">About</a> </li> <li> <a href="#">Services</a> </li> <li> <a href="#">Blog</a> </li> <li> <a href="#">Contact</a> </li> </ul> </div> </div> </div>
</nav>

This is the header HTML without any Tailwind CSS styling. Pretty standard stuff. We’ll wind up moving the “APP LOGO” to the left side, and the four navigation links on the right side of it.

Now let’s add some Tailwind CSS to it:

<nav class="bg-blue-900 shadow-lg"> <div class="container mx-auto"> <div class="sm:flex"> <a href="#" class="text-white text-3xl font-bold p-3">APP LOGO</a> <!-- Menus --> <div class="ml-55 mt-4"> <ul class="text-white sm:self-center text-xl"> <li class="sm:inline-block"> <a href="#" class="p-3 hover:text-red-900">About</a> </li> <li class="sm:inline-block"> <a href="#" class="p-3 hover:text-red-900">Services</a> </li> <li class="sm:inline-block"> <a href="#" class="p-3 hover:text-red-900">Blog</a> </li> <li class="sm:inline-block"> <a href="#" class="p-3 hover:text-red-900">Contact</a> </li> </ul> </div> </div> </div>
</nav>

OK, let’s break down all those classes we just added to the HTML. First, let’s look at the <nav> element:

<nav class="bg-blue-900 shadow-lg">

We apply the class bg-blue-900 gives our header a blue background with a shade of 900, which is dark. The class shadow-lg class applies a large outer box shadow. The shadow effect this class creates will be 0px at the top, 10px on the right, 15px at the bottom, and -3px on the left.

Next is the first div, our container for the logo and navigation links:

<div class="container mx-auto">

To center it and our navigation links, we use the mx-auto class. It’s equivalent to margin: auto, horizontally centering an element within its container.

Onto the next div:

<div class="sm:flex">

By default, a div is a block-level element. We use the sm:flex class to make our header a block-level flex container, so as to make its children responsive (to enable them shrink and expand easily). We use the sm prefix to ensure that the style is applied to all screen sizes (small and above).

Alright, the logo:

<a href="#" class="text-white text-3xl font-bold p-3">APP LOGO</a>

The text-white class, true to its name, make the text of the logo white. The text-3xl class sets the font size of our logo (which is configured to 1.875rem)and its line height (configured to 2.25rem). From there, p-3 sets a padding of 0.75rem on all sides of the logo.

That takes us to:

<div class="ml-55 mt-4">

We’re giving the navigation links a left margin of 55% to move them to the right. However, there’s no Tailwind class for this, so we’ve created a custom style called ml-55, a name that’s totally made up but stands for “margin-left 55%.”

It’s one thing to name a custom class. We also have to add it to our style tags:

.ml-55 { margin-left: 55%;
}

There’s one more class in there: mt-4. Can you guess what it does? If you guessed that it seta a top margin, then you are correct! In this case, it’s configured to 1rem for our navigation links.

Next up, the navigation links are wrapped in an unordered list tag that contains a few classes:

<ul class="text-white sm:self-center text-xl">

We’re using the text-white class again, followed by sm:self-center to center the list—again, we use the sm prefix to ensure that the style is applied to all screen sizes (small and above). Then there’s text-xl which is the extra-large configured font size.

For each list item:

<li class="sm:inline-block">

The sm:inline-block class sets each list item as an inline block-level element, bringing them side-by-side.

And, lastly, the link inside each list item:

<a href="#" class="p-3 hover:text-red-900">

We use the utility class hover:text-red-900 to make each red on hover.

Let’s run our app in the command line:

npm run dev 

This is what we should get:

And that is how we used Tailwind CSS with Svelte in six little steps!

Conclusion

My hope is that you now know how to integrate Tailwind CSS into our Svelte app and configure it. We covered some pretty basic styling, but there’s always more to learn! Here’s an idea: Try improving the project we worked on by adding a sign-up form and a footer to the page. Tailwind provides comprehensive documentation on all its utility classes. Go through it and familiarize yourself with the classes.

Do you learn better with video? Here are a couple of excellent videos that also go into the process of integrating Tailwind CSS with Svelte.

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