webpack.prod.config.js

const path = require('path');
const { merge } = require('webpack-merge');
const MiniCssExtractPlugin = require('mini-css-extract-plugin');
const CssMinimizerPlugin = require('css-minimizer-webpack-plugin');
const common = require('./webpack.common.config');

module.exports = merge(
  common,
  {
    entry: [
      path.join(__dirname, '/client/src/index.jsx'),
      path.join(__dirname, '/client/dist/style.css'),
    ],
    mode: 'production',
    devtool: 'source-map',
    module: {
      rules: [
        {
          test: /.s?css$/i,
          use: [MiniCssExtractPlugin.loader, 'css-loader'],
        },
      ],
    },
    plugins: [new MiniCssExtractPlugin({
      filename: '[name].css',
    })],
    optimization: {
      minimizer: [new CssMinimizerPlugin()],
      minimize: true,
      splitChunks: {
        cacheGroups: {
          styles: {
            name: 'styles',
            test: /\.css$/,
            enforce: true,
          },
        },
      },
    },
  },
);