If you have not yet installed Node.js, check out my article Install Node.js on Linux.

Let's say you have a file named app.js that contains the following.

const url = require("url");

const returnurl = function (req, res) {
  const myurl = new URL(`http://www.example.com:12345/index.html?id=123`);
  return myurl
}

const foo = returnurl();

console.log(foo);

Running app.js should return something like this.

URL {
  href: 'http://www.example.com:12345/index.html?id=123',
  origin: 'http://www.example.com:12345',
  protocol: 'http:',
  username: '',
  password: '',
  host: 'www.example.com:12345',
  hostname: 'www.example.com',
  port: '12345',
  pathname: '/index.html',
  search: '?id=123',
  searchParams: URLSearchParams { 'id' => '123' },
  hash: ''
}

And here is how you could return the non-dictionary keys.

const url = require("url");

const returnhostname = function (req, res) {
  const myurl = new URL(`http://www.example.com:12345/index.html?id=123`);
  return myurl
}

const foo = returnurl();

console.log(foo);

Which in this example should return www.example.com.

~]$ node app.js
www.example.com

And here is how you can return one of the searchParams.

const { URL, URLSearchParams } = require('url');

const return_id = function (req, res) {
  const myurl = new URL(`http://www.example.com:12345/index.html?id=123`);
  return myurl.searchParams.get('id');
}

const id = return_id();

console.log(id);

Which in this example should return 123.

~]$ node app.js
123