webpack.config.js

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

module.exports = {
  entry: './src/index.js',
  output: {
    path: path.resolve(__dirname, 'dist'),
    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$/,
        include: path.resolve(__dirname, 'src'),
        exclude: /(node_modules|bower_components|dist)/,
        use: {
          loader: 'babel-loader',
          options: {
            presets: ['env']
          }
        }
      },
      {
        test: /\.css$/,
        use: [
          'style-loader',
          'css-loader'
        ]
      },
      {
        test: /\.(png|svg|jpg|gif)$/,
        use: {
          loader: 'url-loader',
          options: {
            limit: 102400,
            name: '[name].[ext]'
          }
        }
      }
    ]
  },
  plugins: [
    new webpack.optimize.UglifyJsPlugin({
      compress: {
        warnings: false,
        drop_console: true,
      }
    })
  ],
  externals: {
    'react': 'commonjs react' // this line is just to use the React dependency of our parent-testing-project instead of using our own React.
  }
};