webpack.config.js

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

// Manually configure the runtime environment if not already configured yet by the "encore" command.
// It's useful when you use tools that rely on webpack.config.js file.
if (!Encore.isRuntimeEnvironmentConfigured()) {
  Encore.configureRuntimeEnvironment(process.env.NODE_ENV || 'dev');
}

Encore
  // directory where compiled assets will be stored
  .setOutputPath('public/build/')
  // public path used by the web server to access the output path
  .setPublicPath(process.env.WEBPACK_PUBLIC_PATH || '/build')
  // only needed for CDN's or sub-directory deploy
  .setManifestKeyPrefix('build/')

  /*
   * ENTRY CONFIG
   *
   * Add 1 entry for each "page" of your app
   * (including one that's included on every page - e.g. "app")
   *
   * Each entry will result in one JavaScript file (e.g. app.js)
   * and one CSS file (e.g. app.css) if your JavaScript imports CSS.
   */
  .addEntry('app', './assets/js/app.js')

  // enables the Symfony UX Stimulus bridge (used in assets/bootstrap.js)
  .enableStimulusBridge('./assets/controllers.json')

  // When enabled, Webpack "splits" your files into smaller pieces for greater optimization.
  .splitEntryChunks()

  // will require an extra script tag for runtime.js
  // but, you probably want this, unless you're building a single-page app
  .enableSingleRuntimeChunk()

  /*
   * FEATURE CONFIG
   *
   * Enable & configure other features below. For a full
   * list of features, see:
   * https://symfony.com/doc/current/frontend.html#adding-more-features
   */
  .cleanupOutputBeforeBuild()
  .enableBuildNotifications()
  .enableSourceMaps(!Encore.isProduction())
  // enables hashed filenames (e.g. app.abc123.css)
  .enableVersioning(Encore.isProduction())

  .configureBabel((config) => {
    config.plugins.push('@babel/plugin-proposal-class-properties');
  })

  // enables @babel/preset-env polyfills
  .configureBabelPresetEnv((config) => {
    config.useBuiltIns = 'usage';
    config.corejs = 3;
  })

  .configureDevServerOptions(options => {
    // Watch Twig & yaml files to force reload the browser on changes:
    options.liveReload = true;
    options.watchFiles = [
      'templates/**/*.twig',
      'content/**/*.yaml',
    ];

    // Disable watching the static `public` folder since it would force a live reload on any change,
    // as the manifest.json file is always re-computed (but not required by the dev server):
    options.static.watch = false;
  })

  // enables Sass/SCSS support
  .enableSassLoader()
  .enablePostCssLoader()

  .copyFiles({
    from: './assets/images',
    to: 'images/[path][name].[hash:8].[ext]',
  })

;

module.exports = Encore.getWebpackConfig();