I try to find a simple way to wait for a certain xhr response until I call my function/script.

I'm working with Adobe Target and want to make sure that on a certain page a capability is fully loaded before I start my script. In this case I cannot listen to changes in the DOM, but need to make sure, that a response from a request, I do not activly trigger, is already in place.

Let's say I want to

1. Wait for XHR Response from the url: /api/a
2. Wait for fetch Response from the url: /api/a
3. Wait for a XHR Response and make sure a certain file is loaded (url: /voucher.php)
4. Wait for a fetch Response and make sure a certain file is loaded (url: /voucher.php)

I really can't find a solution on this. I read this article: https://dmitripavlutin.com/catch-the-xmlhttp-request-in-plain-javascript/

— But i simple do not understand how it works and how I define the specific request I would like to listen to.

I hope anyone can help. Thank you!