webpack.config.js

const UglifyJsPlugin = require("uglifyjs-webpack-plugin");
const MiniCssExtractPlugin = require("mini-css-extract-plugin");
const OptimizeCSSAssetsPlugin = require("optimize-css-assets-webpack-plugin");
var path = require("path");

module.exports = {
  entry: path.resolve(__dirname, "./src/js/main.js"),
  output: {
    path: path.resolve(__dirname, "dist"),
    filename: "bundle.js",
    publicPath: "/dist"
  },
  module: {
    rules: [
      {
        test: /\.m?js$/,
        exclude: /(node_modules|bower_components)/,
        use: {
          loader: "babel-loader",
          options: {
            presets: ["@babel/preset-env"]
          }
        }
      },
      {
        test: /\.s?css$/,
        use: [MiniCssExtractPlugin.loader, "css-loader", "sass-loader"]
      }
    ]
  },
  optimization: {
    minimizer: [
      new UglifyJsPlugin({
        cache: true,
        parallel: true,
        sourceMap: true // set to true if you want JS source maps
      }),
      new OptimizeCSSAssetsPlugin({})
    ]
  },
  plugins: [
    new MiniCssExtractPlugin({
      filename: "[name].css",
      chunkFilename: "[id].css"
    })
  ]
};