Example of how a main express app can mount sub-applications on a mount point with app.use('/mount-point', subapp); If you GET /, you'll see the main_app's '/' response. If you GET /ep_app, you'll see the ep_app's '/' response.

ep_app.js

const express = require("express");
const router = express.Router();

router.get('/', function (req, res) {
  res.send("This is the '/' route in ep_app");
});

module.exports = router;

main_app.js

#!/usr/bin/env node
const express = require("express");
const http = require("http");

const mainRouter = express.Router();
const epRouter = require("./ep_app");
const server = express();

mainRouter.get('/', function (req, res) {
  res.send("This is the '/' route in main_app");
});

server.use('/ep_app', epRouter);
server.use('/', mainRouter);

http.createServer(server).listen(3000);

@coolaj86 I updated the gist to incorporate your tips. Thanks! Check back in another 9 years for further tweaks LOL.