Forward proxy in Express

forward-proxy.js

const http = require("http");
const express = require("express");
const app = express();

const HOST = "localhost";
const PORT = 4000;
const PROXY_PORT = 8080;

setupProxy();

function setupProxy() {
  app.all("/v1*", function (req, res) {
    var opts = {
      host: HOST,
      port: PORT,
      path: req.url,
      method: req.method,
      headers: req.headers,
      agent: false,
    };

    var request = http.request(opts);

    request.on("response", function (response) {
      // set status code
      if (response.statusCode) res.status(response.statusCode);

      // set headers
      if (response.headers) res.set(response.headers);

      response.pipe(res);
    });

    req.pipe(request);
  });
}

app.listen(PROXY_PORT, () => {
  console.log(`proxy server listening on port ${PROXY_PORT}`);
  console.log(
    `send request to http://${HOST}:${PROXY_PORT}/v1/* to forward it to http://${HOST}:${PORT}`
  );
});