webpack.config.js

const webpack = require("webpack");
const TerserJSPlugin = require('terser-webpack-plugin');
const MiniCssExtractPlugin = require('mini-css-extract-plugin');
const OptimizeCSSAssetsPlugin = require('optimize-css-assets-webpack-plugin');
const { CleanWebpackPlugin } = require('clean-webpack-plugin');
const path = require ('path');
const purgecss = require('@fullhuman/postcss-purgecss');

module.exports = {
  mode: "production",
  entry: {
    main: './assets/index.js'
  },
  output: {
    filename: '[name].js',
    path: path.resolve(__dirname, '.tmp/dist')
  },
  optimization: {
    minimizer: [new TerserJSPlugin({}), new OptimizeCSSAssetsPlugin({})]
  },
  plugins: [
    new CleanWebpackPlugin(),
    new MiniCssExtractPlugin(),
    new webpack.ProvidePlugin({
      $: "jquery"
    })
  ],
  module: {
    rules: [
      {
        test: /\.(scss)$/,
        use: [{
          loader: MiniCssExtractPlugin.loader,
        }, {
          loader: 'css-loader', // translates CSS into CommonJS modules
        }, {
          loader: 'postcss-loader', // Run postcss actions
          options: {
            plugins: function () { // postcss plugins, can be exported to postcss.config.js
              return [
                purgecss({
                  content: [, './source/results/**/*.erb', './assets/**/*.js'],
                  safelist: {
                    greedy: [/^ct-/, /modal/, /^division-/, /collapsing/, /is-focused/]
                  }
                }),
                require('autoprefixer')
              ];
            }
          }
        }, {
          loader: 'sass-loader' // compiles Sass to CSS
        }]
      }
    ]
  },
  performance: {
    hints: process.env.NODE_ENV === 'production' ? "warning" : false,
    maxEntrypointSize: 307200
  }
}