express + webpack-dev-middleware + webpack-hot-middleware

script1.js

// $/static/script.js

import './script2'

console.log('script1')

if (module.hot) {
  module.hot.accept('./script2', function () {
    console.log("YES")
  });
}

server.js

// $/server.js

const webpack = require("webpack");
const webpackDevMiddleware = require("webpack-dev-middleware");
const webpackHotMiddleware = require("webpack-hot-middleware");
const express = require("express");
const app = express();
const path = require('path');

const compiler = webpack({
  mode: "development",
  entry: {
    './script1.js': ["./static/script1.js", 'webpack-hot-middleware/client'],
  },
  output: {
    filename: '[name]',
    path: path.resolve('[name]'),
    publicPath: '/'
  },
  plugins: [
    new webpack.HotModuleReplacementPlugin()
  ],
  module: {
    rules: [
      {
        test: /\.m?js$/,
        exclude: /(node_modules|bower_components)/,
        use: {
          loader: "babel-loader",
          options: {
            presets: ["@babel/preset-env"],
          },
        },
      },
    ],
  },
});

app.use(webpackDevMiddleware(compiler, {}));
app.use(webpackHotMiddleware(compiler));

app.get("/*", function(req, res) {
  let file = req.path;
  if(file === '/') {
    file = '/index.html'
  }
  res.sendFile(__dirname + `/static${file}`);
});

app.listen(3000, () => console.log("Example app listening on port 3000!"));