webpack.config.js

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

/*
 * We've enabled UglifyJSPlugin for you! This minifies your app
 * in order to load faster and run less javascript.
 *
 * https://github.com/webpack-contrib/uglifyjs-webpack-plugin
 *
 */

const UglifyJSPlugin = require('uglifyjs-webpack-plugin');

module.exports = {
  entry: './src/index',

  output: {
    filename: 'index.js',
    path: path.resolve(__dirname, 'lib/'),
  },

  module: {
    rules: [
      {
        test: /\.js?$/,
        exclude: /node_modules/,
        loader: 'babel-loader',
      },
    ],
  },

  externals: {
    react: {
      root: 'React',
      commonjs2: 'react',
      commonjs: 'react',
      amd: 'react',
      umd: 'react',
    },
    'react-dom': {
      root: 'ReactDOM',
      commonjs2: 'react-dom',
      commonjs: 'react-dom',
      amd: 'react-dom',
      umd: 'react-dom',
    },
  },

  plugins: [new UglifyJSPlugin()],
};