webpack.config.js

const path = require('path');
const webpack = require('webpack');
const BundleTracker = require('webpack-bundle-tracker');

module.exports = {
  context: __dirname,

  entry: './assets/js/index', // entry point of our app. assets/js/index.js should require other js modules and dependencies it needs

  output: {
    path: path.resolve('./assets/bundles/'),
    filename: '[name]-[hash].js',
  },

  plugins: [
    new webpack.HotModuleReplacementPlugin(),
    new BundleTracker({ filename: './webpack-stats.json' }),
  ],

  module: {
    rules: [
      {
        test: /\.jsx?$/,
        exclude: /node_modules/,
        loader: 'babel-loader', // to transform JSX into JS
        options: {
          presets: ['@babel/react', '@babel/env'],
          plugins: [
            '@babel/plugin-proposal-class-properties',
            ['@babel/plugin-proposal-decorators', { legacy: true }],
            '@babel/plugin-proposal-do-expressions',
            '@babel/plugin-proposal-export-default-from',
            '@babel/plugin-proposal-export-namespace-from',
            '@babel/plugin-proposal-function-sent',
            '@babel/plugin-proposal-json-strings',
            '@babel/plugin-proposal-logical-assignment-operators',
            '@babel/plugin-proposal-nullish-coalescing-operator',
            '@babel/plugin-proposal-numeric-separator',
            '@babel/plugin-proposal-optional-chaining',
            ['@babel/plugin-proposal-pipeline-operator', { proposal: 'minimal' }],
            '@babel/plugin-proposal-throw-expressions',
            '@babel/plugin-syntax-dynamic-import',
            '@babel/plugin-syntax-import-meta',
          ],
        },
      },
      {
        test: /\.jsx?$/,
        include: path.resolve('assets/js/'),
        exclude: [path.resolve('node_modules/'), path.resolve('assets/js/__test__/')],
        loader: 'istanbul-instrumenter-loader',
        options: {
          esModules: true,
        },
        enforce: 'post',
      },
    ],
  },

  resolve: {
    modules: ['node_modules', 'bower_components'],
    extensions: ['*', '.js', '.jsx'],
  },
};