serve.mjs

// serve.js
//const esbuild = require("esbuild");
import * as esbuild from 'esbuild'
import * as http from 'http'

const serve = async (servedir, listen) => {
  
  let ctx = await esbuild.context({
    entryPoints: ["./src/index.js"],
    outfile: "./public/assets/app.js",
    bundle: true,
    loader: {
      ".js": "jsx",
    },
    plugins: [],
    define: {
      "process.env.PUBLIC_URL": JSON.stringify(process.env.PUBLIC_URL),}
  })
  
  // Start esbuild's local web server. Random port will be chosen by esbuild.
  // edited to start actually randomly
  const { host, port } = await ctx.serve({
    servedir: "public",
    port: Math.floor(Math.random() * (6000 - 5000 + 1) + 5000) ,
    onRequest: (message) => {console.log(message.method, message.status, message.path)},
  }, {});
  //console.log(port)
  // Create a second (proxy) server that will forward requests to esbuild.
  const proxy = http.createServer((req, res) => {
    // forwardRequest forwards an http request through to esbuid.
    const forwardRequest = (path) => {
      const options = {
        hostname: host,
        port,
        path,
        method: req.method,
        headers: req.headers,
      };

      const proxyReq = http.request(options, (proxyRes) => {
        if (proxyRes.statusCode === 404) {
          // If esbuild 404s the request, assume it's a route needing to
          // be handled by the JS bundle, so forward a second attempt to `/`.
          return forwardRequest("/");
        }

        // Otherwise esbuild handled it like a champ, so proxy the response back.
        res.writeHead(proxyRes.statusCode, proxyRes.headers);
        proxyRes.pipe(res, { end: true });
      });

      req.pipe(proxyReq, { end: true });
    };

    // When we're called pass the request right through to esbuild.
    forwardRequest(req.url);
  });

  // Start our proxy server at the specified `listen` port.
  proxy.listen(listen);
};

// Serves all content from ./dist on :1234.
// If esbuild 404s the request, the request is attempted again
// from `/` assuming that it's an SPA route needing to be handled by the root bundle.
serve("public", 3000);