webpack.config.js

const pkg = require('./package.json');
const path = require('path');

const libraryName = pkg.name;

module.exports = {
  entry: path.join(__dirname, './src/index.js'),
  output: {
    path: path.join(__dirname, './dist'),
    filename: 'index.js',
    library: libraryName,
    libraryTarget: 'umd',
    publicPath: '/dist/',
    umdNamedDefine: true,
  },
  module: {
    rules: [
      {
        test: /\.js$/,
        include: path.resolve(__dirname, 'src'),
        exclude: /(node_modules|bower_components|build)/,
        use: {
          loader: 'babel-loader',
          options: {
            presets: ['env'],
          },
        },
      },
      // Handle .css files
      {
        test: /\.css$/,
        use: ['style-loader', 'css-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',
    },
  },
};