webpack.config.js

var path = require('path');
module.exports = {
  entry: './src/index.js',
  output: {
    path: path.resolve(__dirname, 'lib'),
    filename: 'index.js',
    libraryTarget: 'commonjs2' // THIS IS THE MOST IMPORTANT LINE! :mindblow: I wasted more than 2 days until realize this was the line most important in all this guide.
  },
  module: {
    rules: [
      {
        test: /.js$/,
        include: path.resolve(__dirname, 'src'),
        exclude: /(node_modules|bower_components|lib)/,
        use: {
          loader: 'babel-loader',
          options: {},
        }
      },
      {
        test: /.css$/,
        use: [ 'style-loader', 'css-loader' ]
      },
      {
        test: /.(png|jpg|gif|eot|svg|ttf|woff|woff2)$/,
        use: [
          {
            loader: 'file-loader',
            options: {}  
          }
        ]
      },
    ]
  },
  externals: {
    'react': 'commonjs react' // this line is just to use the React dependency of our parent-testing-project instead of using our own React.
  }
};