Put a wrapper around a script so that it only runs on thank you pages with a donation_KEY and an amount.

wrap_script_for_thank_you_page.js

// Put this text on a new line just after the <script> tag (https://prnt.sc/t4j44d).
var isThankYouPage = document.location.href.indexOf("thank_you") != -1;
var hasDonationKEY = /donate_page_KEY=\d+/.test(document.location.href);
var hasAmount = /amount=\d+/.test(document.location.href);
if (isThankYouPage && hasDonationKey && hasAmount) {
  
// Put this text just before the </script> tag (https://prnt.sc/t4j4il).
}