webpack.prod.js

const merge = require("webpack-merge");
const common = require("./webpack.common.js");
const UglifyJsPlugin = require("uglifyjs-webpack-plugin");
const MiniCssExtractPlugin = require("mini-css-extract-plugin");
const OptimizeCSSAssetsPlugin = require("optimize-css-assets-webpack-plugin");

module.exports = merge(common, {
    optimization: {
        minimizer: [
          new UglifyJsPlugin({
            cache: true,
            parallel: true,
            sourceMap: true
          }),
          new OptimizeCSSAssetsPlugin({})
        ],
      },
    mode: "production",
    devtool: 'source-map',
    plugins: [
        new MiniCssExtractPlugin({
            filename: "[name].css",
            chunkFilename: "[id].css"
        })
    ],
    module: {
        rules: [
          {
            test: /\.css$/,
            use: [
              MiniCssExtractPlugin.loader,
              "css-loader"
            ]
          }
        ]
      }
});