Encore: Setting up your Project

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After installing Encore, your app already has a few files, organized into an assets/ directory:

  • assets/app.js
  • assets/styles/app.css

With Encore, think of your app.js file like a standalone JavaScript application: it will require all of the dependencies it needs (e.g. jQuery or React), including any CSS. Your app.js file is already doing this with a JavaScript import statement:

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// assets/app.js
// ...

import './styles/app.css';

Encore's job (via Webpack) is simple: to read and follow all of the import statements and create one final app.js (and app.css) that contains everything your app needs. Encore can do a lot more: minify files, pre-process Sass/LESS, support React, Vue.js, etc.

Configuring Encore/Webpack

Everything in Encore is configured via a webpack.config.js file at the root of your project. It already holds the basic config you need:

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// webpack.config.js
const Encore = require('@symfony/webpack-encore');

Encore
    // directory where compiled assets will be stored
    .setOutputPath('public/build/')
    // public path used by the web server to access the output path
    .setPublicPath('/build')

    .addEntry('app', './assets/app.js')

    // uncomment this if you want use jQuery in the following example
    .autoProvidejQuery()
;

// ...

The key part is addEntry(): this tells Encore to load the assets/app.js file and follow all of the require() statements. It will then package everything together and - thanks to the first app argument - output final app.js and app.css files into the public/build directory.

To build the assets, run the following if you use the npm package manager:

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# compile assets and automatically re-compile when files change
$ npm run watch

# or, run a dev-server that can sometimes update your code without refreshing the page
$ npm run dev-server

# compile assets once
$ npm run dev

# on deploy, create a production build
$ npm run build

All of these commands - e.g. dev or watch - are shortcuts that are defined in your package.json file.

Tip

If you're using the Symfony CLI tool, you can configure workers to be automatically run along with the webserver. You can find more information in the Symfony CLI Workers documentation.

Warning

Whenever you make changes in your webpack.config.js file, you must stop and restart encore.

Congrats! You now have three new files:

  • public/build/app.js (holds all the JavaScript for your "app" entry)
  • public/build/app.css (holds all the CSS for your "app" entry)
  • public/build/runtime.js (a file that helps Webpack do its job)

Note

In reality, you probably have a few more files in public/build. Some of these are due to code splitting, an optimization that helps performance, but doesn't affect how things work. Others help Encore do its work.

Next, to include these in your base layout, you can leverage two Twig helpers from WebpackEncoreBundle:

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{# templates/base.html.twig #}
<!DOCTYPE html>
<html>
    <head>
        <!-- ... -->

        {% block stylesheets %}
            {# 'app' must match the first argument to addEntry() in webpack.config.js #}
            {{ encore_entry_link_tags('app') }}

            <!-- Renders a link tag (if your module requires any CSS)
                 <link rel="stylesheet" href="/build/app.css"> -->
        {% endblock %}

        {% block javascripts %}
            {{ encore_entry_script_tags('app') }}

            <!-- Renders app.js & a webpack runtime.js file
                <script src="/build/runtime.js" defer></script>
                <script src="/build/app.js" defer></script>
                See note below about the "defer" attribute -->
        {% endblock %}
    </head>

    <!-- ... -->
</html>

That's it! When you refresh your page, all of the JavaScript from assets/app.js - as well as any other JavaScript files it included - will be executed. All the CSS files that were required will also be displayed.

The encore_entry_link_tags() and encore_entry_script_tags() functions read from a public/build/entrypoints.json file that's generated by Encore to know the exact filename(s) to render. This file is especially useful because you can enable versioning or point assets to a CDN without making any changes to your template: the paths in entrypoints.json will always be the final, correct paths. And if you use splitEntryChunks() (where Webpack splits the output into even more files), all the necessary script and link tags will render automatically.

If you are not using Symfony you won't have the encore_entry_* functions available. Instead, you can point directly to the final built files or write code to parse entrypoints.json manually. The entrypoints file is needed only if you're using certain optional features, like splitEntryChunks().

1.9.0

The defer attribute on the script tags delays the execution of the JavaScript until the page loads (similar to putting the script at the bottom of the page). The ability to always add this attribute was introduced in WebpackEncoreBundle 1.9.0 and is automatically enabled in that bundle's recipe in the config/packages/webpack_encore.yaml file. See WebpackEncoreBundle Configuration for more details.

Requiring JavaScript Modules

Webpack is a module bundler, which means that you can import other JavaScript files. First, create a file that exports a function, class or any other value:

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// assets/greet.js
export default function(name) {
    return `Yo yo ${name} - welcome to Encore!`;
};

We'll use jQuery to print this message on the page. Install it via:

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$ npm install jquery --save-dev

Great! Use import to import jquery and greet.js:

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// assets/app.js
  // ...

+ // loads the jquery package from node_modules
+ import $ from 'jquery';

+ // import the function from greet.js (the .js extension is optional)
+ // ./ (or ../) means to look for a local file
+ import greet from './greet';

+ $(document).ready(function() {
+     $('body').prepend('<h1>'+greet('jill')+'</h1>');
+ });

That's it! If you previously ran encore dev --watch, your final, built files have already been updated: jQuery and greet.js have been automatically added to the output file (app.js). Refresh to see the message!

Stimulus & Symfony UX

As simple as the above example is, instead of building your application inside of app.js, we recommend Stimulus: a small JavaScript framework that makes it easy to attach behavior to HTML. It's powerful, and you will love it! Symfony even provides packages to add more features to Stimulus. These are called the Symfony UX Packages.

To use Stimulus, first install StimulusBundle:

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$ composer require symfony/stimulus-bundle

The Flex recipe should add several files/directories:

  • assets/bootstrap.js - initializes Stimulus;
  • assets/controllers/ - a directory where you'll put your Stimulus controllers;
  • assets/controllers.json - file that helps load Stimulus controllers form UX packages that you'll install.

Let's look at a simple Stimulus example. In a Twig template, suppose you have:

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<div {{ stimulus_controller('say-hello') }}>
    <input type="text" {{ stimulus_target('say-hello', 'name') }}>

    <button {{ stimulus_action('say-hello', 'greet') }}>
        Greet
    </button>

    <div {{ stimulus_target('say-hello', 'output') }}></div>
</div>

The stimulus_controller('say-hello') renders a data-controller="say-hello" attribute. Whenever this element appears on the page, Stimulus will automatically look for and initialize a controller called say-hello-controller.js. Create that in your assets/controllers/ directory:

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// assets/controllers/say-hello-controller.js
import { Controller } from '@hotwired/stimulus';

export default class extends Controller {
    static targets = ['name', 'output']

    greet() {
      this.outputTarget.textContent = `Hello, ${this.nameTarget.value}!`
    }
}

The result? When you click the "Greet" button, it prints your name! And if more {{ stimulus_controller('say-hello') }} elements are added to the page - like via Ajax - those will instantly work: no need to reinitialize anything.

Ready to learn more about Stimulus?

Turbo: Lightning Fast Single-Page-Application Experience

Symfony comes with tight integration with another JavaScript library called Turbo. Turbo automatically transforms all link clicks and form submits into an Ajax call, with zero (or nearly zero) changes to your Symfony code! The result? You get the speed of a single page application without having to write any JavaScript.

To learn more, check out the symfony/ux-turbo package.

Screencast

Or check out the Turbo Screencast on SymfonyCasts.

Page-Specific JavaScript or CSS

So far, you only have one final JavaScript file: app.js. Encore may be split into multiple files for performance (see split chunks), but all of that code is still downloaded on every page.

What if you have some extra JavaScript or CSS (e.g. for performance) that you only want to include on certain pages?

Lazy Controllers

One very nice solution if you're using Stimulus is to leverage lazy controllers. To activate this on a controller, add a special stimulusFetch: 'lazy' above your controller class:

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// assets/controllers/lazy-example-controller.js
import { Controller } from '@hotwired/stimulus';

/* stimulusFetch: 'lazy' */
export default class extends Controller {
    // ...
}

That's it! This controller's code - and any modules that it imports - will be split to separate files by Encore. Then, those files won't be downloaded until the moment a matching element (e.g. <div data-controller="lazy-example">) appears on the page!

Note

If you write your controllers using TypeScript, make sure removeComments is not set to true in your TypeScript config.

Multiple Entries

Another option is to create page-specific JavaScript or CSS (e.g. checkout, account, etc.). To handle this, create a new "entry" JavaScript file for each page:

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// assets/checkout.js
// custom code for your checkout page
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// assets/account.js
// custom code for your account page

Next, use addEntry() to tell Webpack to read these two new files when it builds:

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// webpack.config.js
  Encore
      // ...
      .addEntry('app', './assets/app.js')
+     .addEntry('checkout', './assets/checkout.js')
+     .addEntry('account', './assets/account.js')
      // ...

And because you just changed the webpack.config.js file, make sure to stop and restart Encore:

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$ npm run watch

Webpack will now output a new checkout.js file and a new account.js file in your build directory. And, if any of those files require/import CSS, Webpack will also output checkout.css and account.css files.

Finally, include the script and link tags on the individual pages where you need them:

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{# templates/.../checkout.html.twig #}
  {% extends 'base.html.twig' %}

+ {% block stylesheets %}
+     {{ parent() }}
+     {{ encore_entry_link_tags('checkout') }}
+ {% endblock %}

+ {% block javascripts %}
+     {{ parent() }}
+     {{ encore_entry_script_tags('checkout') }}
+ {% endblock %}

Now, the checkout page will contain all the JavaScript and CSS for the app entry (because this is included in base.html.twig and there is the {{ parent() }} call) and your checkout entry. With this, JavaScript & CSS needed for every page can live inside the app entry and code needed only for the checkout page can live inside checkout.

Using Sass/LESS/Stylus

You've already mastered the basics of Encore. Nice! But, there are many more features that you can opt into if you need them. For example, instead of using plain CSS you can also use Sass, LESS or Stylus. To use Sass, rename the app.css file to app.scss and update the import statement:

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// assets/app.js
- import './styles/app.css';
+ import './styles/app.scss';

Then, tell Encore to enable the Sass preprocessor:

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// webpack.config.js
  Encore
      // ...

+    .enableSassLoader()
  ;

Because you just changed your webpack.config.js file, you'll need to restart Encore. When you do, you'll see an error!

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>   Error: Install sass-loader & sass to use enableSassLoader()

Encore supports many features. But, instead of forcing all of them on you, when you need a feature, Encore will tell you what you need to install. Run:

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$ npm install sass-loader@^13.0.0 sass --save-dev
$ npm run watch

Your app now supports Sass. Encore also supports LESS and Stylus. See CSS Preprocessors: Sass, etc. with Webpack Encore.

Compiling Only a CSS File

Warning

Using addStyleEntry() is supported, but not recommended. A better option is to follow the pattern above: use addEntry() to point to a JavaScript file, then require the CSS needed from inside of that.

If you want to only compile a CSS file, that's possible via addStyleEntry():

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// webpack.config.js
Encore
    // ...

    .addStyleEntry('some_page', './assets/styles/some_page.css')
;

This will output a new some_page.css.

Keep Going!

Encore supports many more features! For a full list of what you can do, see Encore's index.js file. Or, go back to list of Frontend articles.

This work, including the code samples, is licensed under a Creative Commons BY-SA 3.0 license.
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