webpack.server.js

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

module.exports = {
  // Inform webpack that we're building a bundle
  // for nodeJS, rather than for the browser
  target: 'node',

  // Tell webpack the root file of our
  // server application
  entry: './server/index.js',

  mode: 'development',

  // Tell webpack where to put the output file
  // that is generated
  output: {
    filename: 'bundle.js',
    path: path.resolve(__dirname, 'server-build')
  },

  externals: [webpackNodeExternals()],

  // Tell webpack to run babel on every file it runs through
  module: {
    rules: [
      {
        test: /\.js?$/,
        loader: 'babel-loader',
        exclude: /node_modules/
      }
    ]
  }
};