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 CleanWebpackPlugin = require("clean-webpack-plugin");
const path = require("path");

module.exports = merge(common, {
  mode: "production",
  watch: false,
  output: {
    path: path.resolve(__dirname, "build"),
    filename: "js/script.js"
  },

  optimization: {
    minimizer: [
      new UglifyJsPlugin({
        cache: true,
        parallel: true
      })
    ]
  },
  plugins: [
    new CleanWebpackPlugin(),
    new MiniCssExtractPlugin({
      filename: "css/style.css"
    })
  ],
  module: {
    rules: [
      { test: /\.js$/, loader: "babel-loader" },
      {
        test: /\.(sa|sc|c)ss$/,
        use: [
          {
            loader: MiniCssExtractPlugin.loader
          },
          "css-loader",
          {
            loader: "postcss-loader",
            options: {
              plugins: function() {
                return [require("autoprefixer")];
              }
            }
          },
          "sass-loader"
        ]
      }
    ]
  }
});