Improve prevent-xhr scriptlet

[AdamWr]

There is a website - AdguardTeam/AdguardFilters#111383 which detects adblockers when googletagmanager.com/gtag/ (xmlhttprequest) is blocked.

Unfortunately, streamingcommunity.site#%#//scriptlet('prevent-xhr', 'googletagmanager.com') doesn't work correctly in this case and video player is broken.

If I'm not wrong, it's because website uses loadend event, so I guess that adding:

const loadEndEvent = new Event('loadend');
thisArg.dispatchEvent(loadEndEvent);

here:

Scriptlets/src/scriptlets/prevent-xhr.js

Lines 128 to 134 in 8877b08

	setTimeout(() => {
	const stateEvent = new Event('readystatechange');
	thisArg.dispatchEvent(stateEvent);
	const loadEvent = new Event('load');
	thisArg.dispatchEvent(loadEvent);
	}, 1);

should fixes this issue.

[ameshkov]

Makes perfect sense, thank you!

More info on the XHR events:
https://developer.mozilla.org/en-US/docs/Web/API/XMLHttpRequest#events

[AdamWr]

By the way, maybe we could also add additional option to generate random responseText?

Scriptlets/src/scriptlets/prevent-xhr.js

Line 121 in 8877b08

responseText: { value: '', writable: false },

As I recall, there was a website which was checking if responseText === "".

Steps to reproduce:

1. Add this rule:

example.org#%#//scriptlet('prevent-xhr', 'pagead2.googlesyndication.com')

2. Go to - https://example.org/
3. Run this script:

(() => {
  function reqListener() {
    if (this.status !== 200 || this.responseText === "") {
      alert("adblock");
    } else {
      (() => {
        let video = '<iframe width="560" height="315" src="https://www.youtube.com/embed/Fy2rtb95QhY" title="YouTube video player" frameborder="0" allow="accelerometer; autoplay; clipboard-write; encrypted-media; gyroscope; picture-in-picture" allowfullscreen></iframe>';
        let createDiv = document.createElement("div");
        document.body.appendChild(createDiv);
        createDiv.innerHTML = video;
      })();
    }
  }

  var oReq = new XMLHttpRequest();
  oReq.addEventListener("load", reqListener);
  oReq.open("GET", "https://pagead2.googlesyndication.com/pagead/js/adsbygoogle.js");
  oReq.send();
})();

Alert will be displayed, because this.responseText returns "".
If pagead2.googlesyndication.com/pagead/js/adsbygoogle.js is not blocked then video player is loaded.

[uBlock-user]

@gorhill Need to do the same for no-xhr-if.js