webpack.config.js

const path = require("path");
const WebpackNodeExternals = require('webpack-node-externals')

const commonConfiguration = {
  mode: process.env.NODE_ENV || "development",
}
const moduleBabel = {
  test: /index\.js$/,
  exclude: /node_modules/,
  use: {
    loader: "babel-loader",
  }
}

module.exports = [
  {
    ...commonConfiguration,
    entry: "./source/client/index.js",
    target: "web",
    output: {
      path: path.resolve(__dirname, "tmp"),
      filename: "client.js"
    },
    module: {
      rules: [
        moduleBabel
      ]
    }
  },
  {
    ...commonConfiguration,
    entry: "./source/server/index.js",
    target: "node",
    externals: [
      WebpackNodeExternals()
    ],
    output: {
      path: path.resolve(__dirname, "tmp"),
      filename: "server.js",
      libraryTarget: "commonjs2"
    },
    module: {
      rules: [
        moduleBabel
      ]
    }
  }
]