webpack.config.js

const path = require('path');
const TerserPlugin = require("terser-webpack-plugin");
const CopyPlugin = require("copy-webpack-plugin");
const ConcatPlugin = require('@mcler/webpack-concat-plugin');
const JsonMinimizerPlugin = require("json-minimizer-webpack-plugin");
const CssMinimizerPlugin = require("css-minimizer-webpack-plugin");

module.exports = env => ({
  /// background script
  entry: {
    background: "./src/functions/background.js"
  },
  output: {
    path: path.resolve(__dirname, 'dist'),
    filename: "[name].js"
  },
  plugins: [
    /// content scripts
    new ConcatPlugin({
      name: 'content',
      outputPath: './',
      fileName: '[name].js',
      filesToConcat: [
        "./src/data/**",
        [
          "./src/functions/**",
          "!./src/functions/background.js",
        ],
        "./src/ui/**/**",
        "./src/index.js",
      ]
    }),
    /// static files
    new CopyPlugin({
      patterns: [
        "src/index.css",
        { from: "src/_locales", to: "_locales" },
        { from: "src/assets", to: "assets" },
        { from: "src/popup", to: "popup" },
        { from: "src/options", to: "options" },
        /// additional dependencies for toolbar popup and options page
        { from: "src/data/configs.js", to: "src/data/" },
        { from: "src/data/currencies.js", to: "src/data/" },

        // { from: "src/manifest.json", to: "manifest.json" },
        ... env.build == 'chrome' ? [
          { 
            from: "src/manifest.json", 
            to: "manifest.json",
            transform(content, absoluteFrom) {
              const manifest = JSON.parse(content.toString());

              /// Remove background.scripts (from manifest v2)
              delete manifest['background']['scripts'];
              return JSON.stringify(manifest);
            },
          }
        ] : [
          { from: "src/manifest.json", to: "manifest.json" }
        ],
      ],
    }),
  ],
  mode: 'production',
  optimization: {
    minimize: true,
    minimizer: [
      new TerserPlugin(), 
      new CssMinimizerPlugin(),
      new JsonMinimizerPlugin(),
    ],
  },
});