webpack.prod.js

const {merge} = require("webpack-merge");
const UglifyJsPlugin = require("uglifyjs-webpack-plugin");
const OptimizeCSSAssetsPlugin = require("optimize-css-assets-webpack-plugin");
const MiniCssExtractPlugin = require("mini-css-extract-plugin");

const common = require("./webpack.common.js");

module.exports = merge(common, {
  mode: "production",

  module: {
    rules: [
      {
        test: /\.(sa|sc|c)ss$/,
        exclude: /node_modules/,
        use: [MiniCssExtractPlugin.loader, "css-loader", "postcss-loader", "sass-loader"]
      }
    ]
  },

  output: {
    filename: "[name].[hash:5].js",
    chunkFilename: "[id].[hash:5].css"
  },

  optimization: {
    minimizer: [
      new UglifyJsPlugin({
        cache: true,
        parallel: true,
        sourceMap: true
      }),

      new MiniCssExtractPlugin({
        filename: "[name].[hash:5].css",
        chunkFilename: "[id].[hash:5].css"
      }),

      new OptimizeCSSAssetsPlugin({})
    ]
  }
});