gist for express server to serve some registered urls from self and others from proxy

proxy_express_server.js

const express = require('express');
const httpProxy = require('http-proxy');

const app = express();
const proxy = httpProxy.createProxyServer();
const port = 3001;
const serverBehindProxy = 'https://a.b.c';
// const serverBehindProxy = 'http://localhost:3000';

const pathsAvailableOnWebsite = {
  "":true, // root path (http://localhost:3001/base-url-for-proxy; in this case) to be served from the website and not from the proxy
  "path-available-on-website-1" :true, // to be served from website angular
  "path-available-on-website-2" :true, // to be served from website angular
}

app.get('/', (req, res) => {
  res.send('Hello World! From proxy server root');
});

// add middleware for interception
app.use('/base-url-for-proxy*', (req, res, next) => {
  // uncomment for debugging
  // console.log("middleware invoked");
  // console.log('Request Type:', req.method);
  // console.log('requested path:', req.path);
  // console.log('requested baseUrl:', req.baseUrl); // url without params and stripped of the mount path
  // console.log('requested originalUrl:', req.originalUrl);
  
  // if path not reserved to be served from the website;
  // proxy to wordpress server
  const subDirAfterOCC = req.baseUrl.replace("/base-url-for-proxy", "").replace("/", ""); // cascaded to handle root path
  if (!pathsAvailableOnWebsite[subDirAfterOCC]) {
    // console.log("path not available on website, try to server from proxy");
    // console.log(`trying target:  ${serverBehindProxy}${req.originalUrl}`);
    proxy.web(req, res, { 
      target: `${serverBehindProxy}${req.originalUrl}`,
      // secure: false,
      // toProxy: true, // what stupidity is this ??? the options do not work as documented
      // prependPath: true,
      ignorePath: true, // this needs to be true if express is setting the req.url to / for file req making them look like directory req
      changeOrigin: true,
      xfwd: true
    }, (err) => {
      console.log("error proxy serving the request :(", err);
    });
  } else {
    console.log("path available on website, let angular serve it, do nothing");
    next();
  }
});


// app.get('/base-url-for-proxy*', (req, res) => {
//   res.send('Hello World! From proxy server base path');
// });

app.get('*', (req, res) => {
  res.send('Hello World! From catch-all path');
});


app.listen(port, () => {
  console.log(`Example app listening on port ${port}`);
});

trial_express_server_behind_proxy.js

const express = require('express');
const app = express();
const port = 3000;

app.get('/', (req, res) => {
  console.log("original url", req.originalUrl);
  res.send('Hello World! From the base express server behind the proxy');
});

app.get('*', (req, res) => {
  console.log("original url", req.originalUrl);
  res.send('Hello World! From the catch-all path of base express server behind the proxy');
  console.log("req headers:", req.headers);
});



app.listen(port, () => {
  console.log(`Example app listening on port ${port}`);
});