webpack.server.config.js

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

module.exports = (env, argv) => {

  const SERVER_PATH = (argv.mode === "production") ?
    "./src/server/server-prod.ts" :
    "./src/server/server-dev.ts";

  const OUTPUT_PATH = (argv.mode === "production") ?
    path.join(__dirname, 'dist_prod') :
    path.join(__dirname, 'dist_dev');

  return ({
    entry: {
      server: SERVER_PATH,
    },
    output: {
      path: OUTPUT_PATH,
      filename: 'server.js'
    },
    target: 'node',
    node: {
      // Need this when working with express, otherwise the build fails
      __dirname: false,   // if you don't put this is, __dirname
      __filename: false,  // and __filename return blank or /
    },
    resolve: {
      extensions: [".ts", ".js"]
    },
    externals: [nodeExternals()], // Need this to avoid error when working with Express
    module: {
      rules: [
        {
          test: /\.ts$/,
          exclude: /node_modules/,
          use: [
            {
              loader: "ts-loader"
            }
          ]
        }
      ]
    }
  });
}