Sometimes you want to randomly assign a port to a NodeJS/Express process instead of a hardcoded port.
To randomly assign a port in Node simply listen on port '0'.
const express = require('express');
const app = express();
// Listen on random port
------
const server = app.listen(0, ()=>{
console.log(`Server listening on port: ${server.address().port}`); // Server listening on port 59813
});