Using Webpack/Laravel-Mix to bundle/compile Drupal 8 Theme assets.

webpack.mix.js

const { mix } = require('laravel-mix')
const path = require('path')

/*
 |--------------------------------------------------------------------------
 | Asset Management
 |--------------------------------------------------------------------------
 |
 | This file defines the building steps of the application. Here's where the
 | client-side technologies are configured according to the needs. Steps such
 | as JSX or SASS processing also happens here.
 |
 | In our case, we're using laravel mix to manage most of the hassle of manually
 | setting theses rules. We're also using a custom webpack config which allows
 | us to add any additional babel plugin that we may need (such as babel decorators).
 |
 */

mix
    .browserSync({
        open: false,
        proxy: 'drupal8theming.test',
        notify: false,
        stream: true,
        files: [
            'style.css',
            'js/{*,**/*}.js',
            '{*,**/*}.php'
        ]
    })
    .options({
        processCssUrls: false
    })
    .webpackConfig({
        resolve: {
            modules: [
                path.resolve('./assets/scripts'),
                path.resolve('./node_modules')
            ],
        }
    })
    .sass('assets/scss/application.scss', 'css/application.css')
    .js('assets/scripts/application.js', 'js/application.js')