webpack.prod.js

const {CleanWebpackPlugin} = require('clean-webpack-plugin');
const {BundleAnalyzerPlugin} = require('webpack-bundle-analyzer');
const {merge} = require('webpack-merge');
const common = require('./webpack.common');

module.exports = merge(common, {
  mode: 'production',
  optimization: { // New object for Bundle Optimization & Code Splitting
    splitChunks: {
      chunks: 'all',
      minSize: 20000, // Minimal size bundle
      maxSize: 70000, // Maximal size bundle
      minChunks: 1,
      maxAsyncRequests: 30,
      maxInitialRequests: 30,
      automaticNameDelimiter: '~',
      enforceSizeThreshold: 50000,
      cacheGroups: {
        defaultVendor: {
          test: /[\\/]node_modules[\\/]/,
          priority: -10,
        },
        default: {
          minChunks: 2,
          priority: -20,
          reuseExistingChunk: true,
        },
      },
    },
  },
  module: {
    rules: [
      {
        test: /\.js$/,
        exclude: '/node_modules/',
        use: [
          {
            loader: 'babel-loader',
            options: {
              presets: ['@babel/preset-env'],
            },
          },
        ],
      },
    ],
  },
  plugins: [
    new CleanWebpackPlugin(),
    new BundleAnalyzerPlugin({
      analyzerMode: 'disabled',
      generateStatsFile: true,
      statsOptions: {source: false},
    }),
  ],
});