Grab query string value from URL using Javascript

I want to visit https://example.com/?GCLID=test123 and store whatever is in GCLID in a variable.

How do I do this? The following keeps returning null

var url = window.location.href;

// test
url = "https://example.com/?GCLID=test123";

const params = new URLSearchParams(url);
var gclid = params.get('GCLID');

alert(params);
alert(gclid);

Answer

You have to take the part after ‘?’ in new URLSearchParams, see below example for same, i.e you will pass window.location.search like this

const params = new URLSearchParams(window.location.search);

var url = window.location.href;

// test
url = "https://example.com/?GCLID=test123";

const params = new URLSearchParams(url.split('?')[1]);
var gclid = params.get('GCLID');

alert(params);
alert(gclid);