webpack.config.js

const webpack = require('webpack');
const path = require('path');

module.exports = {
  mode: 'production',
  entry: './src/index.js',
  output: {
    path: path.resolve(__dirname, 'build'),
    filename: 'index.js',
    globalObject: 'this',
    libraryTarget: 'umd',
  },
  module: {
    rules: [
      {
        test: /\.(js|jsx)$/,
        exclude: /node_modules/,
        use: {
          loader: 'babel-loader',
        }
      },
      {
        test: /\.js$/,
        include: path.resolve(__dirname, 'src'),
        exclude: /(node_modules|build)/,
        use: ['babel-loader', 'eslint-loader']
      }
    ]
  },
  resolve: {
    alias: {
      react: path.resolve(__dirname, './node_modules/react'),
      'react-dom': path.resolve(__dirname, './node_modules/react-dom'),
    },
  },
  externals: {
    // don't bundle react or react-dom
    react: {
      commonjs: "react",
      commonjs2: "react",
      amd: "React",
      root: "React",
    },
    "react-dom": {
      commonjs: "react-dom",
      commonjs2: "react-dom",
      amd: "ReactDOM",
      root: "ReactDOM",
    },
  },
};