webpack.config.js

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

const config = {
  // in development,
  // 'webpack-dev-server/client' and 'webpac/hot/dev-server' will be automatically added
  entry: [
    './src/index.js'
  ],
  output: {
    path: path.resolve(__dirname, 'build'),
    filename: 'app.js',
    publicPath: '/'
  },
  module: {
    rules: [
      {
        test: /\.jsx?$/,
        include: [
          path.resolve(__dirname, 'src')
        ],
        loader: 'babel-loader'
      },
      {
        test: /\.css$/,
        use: [
          {
            loader: 'style-loader',
          },
          {
            loader: 'css-loader',
          }
        ]
      }
    ]
  }
}

if (process.env.NODE_ENV === 'production') {

  config.devtool = 'source-map'

  // Exclude react and react-dom in the production bundle
  config.externals = {
    'react': 'React',
    'react-dom': 'ReactDOM'
  }

} else {

  config.devtool = 'cheap-module-source-map'

  config.devServer = {
    contentBase: path.resolve(__dirname, 'public'),
    clientLogLevel: 'none',
    quiet: true,
    port: 8000,
    compress: true,
    hot: true,
    historyApiFallback: {
      disableDotRule: true
    }
  }

  // HMR support
  config.plugins = [
    new webpack.HotModuleReplacementPlugin(),
    new webpack.NamedModulesPlugin()
  ]
}

module.exports = config