webpack.config.js

var path = require('path')
var webpack = require('webpack')
var nodeExternals = require('webpack-node-externals')

var clientConfig = {
  entry: './src/client.js',
  output: {
    path: path.resolve(__dirname, 'public'),
    filename: 'bundle.js',
    publicPath: '/'
  },
  module: {
    rules: [
      { test: /\.(js|jsx)$/, use: 'babel-loader' }
    ]
  },
  resolve: {
    extensions: ['*', '.js', '.jsx']
  },
  plugins: [
    new webpack.DefinePlugin({
      __isBrowser__: "true"
    })
  ]
}

var serverConfig = {
  entry: './src/server.js',
  target: 'node',
  externals: [nodeExternals()],
  output: {
    path: __dirname,
    filename: 'server.js',
    publicPath: '/'
  },
  module: {
    rules: [
      { test: /\.(js|jsx)$/, use: 'babel-loader' }
    ]
  },
  resolve: {
    extensions: ['*', '.js', '.jsx']
  },
  plugins: [
    new webpack.DefinePlugin({
      __isBrowser__: "false"
    })
  ]
}

module.exports = [clientConfig, serverConfig]