webpack.config.js

const path = require('path'),
  webpack = require('webpack'),
  CompressionPlugin = require('compression-webpack-plugin');

const APP_DIR = path.resolve(__dirname, 'src');
const BUILD_DIR = path.resolve(__dirname, 'dist');
const env = process.env.NODE_ENV || 'development';

module.exports = {
  entry: `${APP_DIR}/index.js`,
  output: {
    path: BUILD_DIR,
    filename: env === 'production' ? '[name].[chunkhash].js' : '[name].js',
  },
  plugins: [
    new webpack.DefinePlugin({
      'process.env': {
        NODE_ENV: JSON.stringify(env),
      },
    }),
    new CompressionPlugin({
      filename: '[path].gz[query]',
      algorithm: 'gzip',
      test: /\.(js|html)$/,
      threshold: 10240,
      minRatio: 0.8,
    }),
  ],
  module: {
    rules: [
      {
        test: /\.jsx?/,
        include: APP_DIR,
        use: {
          loader: 'babel-loader',
          options: {
            babelrc: false,
            presets: [
              '@babel/preset-env',
              '@babel/preset-react',
            ],
            plugins: [
              '@babel/plugin-proposal-class-properties',
            ],
          },
        },
      },
      {
        test: /\.(css|scss)$/,
        use: [
          'style-loader',
          'css-loader',
          'sass-loader',
        ],
      },
    ],
  },
};