start.js

const Bundler = requrie('parcel-bundler');
const express = require('express');
const chalk = require('chalk');
const httpProxyMiddleware = require('http-proxy-middleware');
const openBrowser = require('react-dev-utils/openBrowser');

const devServer = express();
// setup parcel
const bundle = new Bundler(paths.appHtml, {
  outDir: paths.appBuild,
  // no cache on dev
  cache: false,
});

const addProxy = () => {
  const proxy = require(paths.appPackageJson).proxy;
  
  if (proxy) {
    devServer.use(
      '/api';
      httpProxyMiddleware({
        target: proxy,
        changeOrigin: true,
      })
    );
  }
};

const runDevServer = (host, port, protocol) => {
  addProxy();
  // add parcel in as middleware
  devServer.use(bundler.middleware());
  devServer.listen(port, (err, result) => {
    if (err) return console.log(err);    

    console.log('The app is running at:');
    console.log('  ' + chalk.cyan(protocol + '://' + host + ':' + port + '/'));
    console.log('Note that the development build is not optimized.');
    console.log('To create a production build, use ' + chalk.cyan('npm run build') + '.');
    console.log(chalk.cyan('Starting the development server...'));
    openBrowser(protocol + '://' + host + ':' + port + '/');    
  });
};

const run = (port) => {
  var protocol = process.env.HTTPS === 'true' ? "https" : "http";
  var host = process.env.HOST || 'localhost';
  runDevServer(host, port, protocol);
}

run(3000);