webpack.config.js

const path = require('path')
const HtmlWebpackPlugin = require('html-webpack-plugin')
const MiniCssExtractPlugin = require('mini-css-extract-plugin')
const CopyWebpackPlugin = require('copy-webpack-plugin')

var webpack = require('webpack');
var DuplicatePackageCheckerPlugin = require("duplicate-package-checker-webpack-plugin");
const TerserPlugin = require("terser-webpack-plugin");

module.exports = {
  entry: path.join(__dirname, 'src', 'index.js'),
  output: {
    path: path.join(__dirname, 'build'),
    filename: 'bundle.js',
  },
  optimization: {
    minimize: true,
    minimizer: [new TerserPlugin()],
  },
  module: {
    rules: [
      {
        test: /.(js|jsx)$/,
        exclude: /node_modules/,
        use: {
          loader: 'babel-loader',
        },
      },
      {
        test: /.(css|scss)$/,
        use: [MiniCssExtractPlugin.loader, 'css-loader', 'sass-loader'],
      },
      {
        test: /.(jpg|jpeg|png|gif|mp3|svg)$/,
        use: [
          {
            loader: 'file-loader',
            options: {
              name: '[path][name]-[hash:8].[ext]',
            },
          },
        ],
      },
      {
        test: /\.(png|jpe?g|gif)$/i,
        loader: 'file-loader',
        options: {
          name: '[path][name].[ext]',
        },
      },
      {
        test: /\.(woff|woff2|eot|ttf|otf)$/,
        use: [{
          loader: 'file-loader',
          options: {
            name: '[name].[hash:4].[ext]'
          }
        }]
      },
    ],
  },
  plugins: [
    new webpack.DefinePlugin({ // <-- key to reducing React's size
      'process.env': {
        'NODE_ENV': JSON.stringify('production')
      }
    }),
    new DuplicatePackageCheckerPlugin(),
    new webpack.optimize.AggressiveMergingPlugin(),//Merge chunks 
    new CopyWebpackPlugin({
      patterns: [
        {
          from: path.join(process.cwd(), 'static'),
          to: path.join(process.cwd(), 'build'),
        },
      ],
    }),
    new HtmlWebpackPlugin({
      filename: 'index.html',
      template: path.join(__dirname, 'src', 'index.html'),
    }),
    new MiniCssExtractPlugin({
      filename: '[name].css',
      chunkFilename: '[id].css',
    }),
  ],
}