How to get over a blocked event?

Question

I'm developing an JavaScript app which needs to trigger mousemove event, and I am using tampermonkey to "embed" it on websites to test if it works on them. On one website, the mousemove event is simply blocked (I don't know why) and even console.log within this event doesn't show. It seems like this event has never triggered (the website ignores).

Is it possible to "override" events and block them? If so, how can I override this action and enable my specific mousemove event?

This script won't work:

document.addEventListener("mousemove", function(e) {
    e = e || window.event;
    e.stopPropagation();
    console.log("[HELLO] Is it moving?!");
}, false);

(the result will be... nothing. this won't be logged)

Update They set window.onmousemove as null. Is there any way to revert this?

also if you're running your code on random sites it is possible that for whatever reason the js on the site is removing event handlers on an interval or something causing your mouse move not to fire (first answer is much more likely) — bturner1273, Apr 12 '22 at 13:11

score 0 · Answer 1 · answered Apr 12 '22 at 13:09

0

If some other event handler called stopPropagation() on the event, it won't be propagated up to the document level during the "bubble" phase.

However, you can make your event handler be called sooner, by running it in the "capture" phase. Simply change the third argument from false to true. This will solve most issues, except if some other event handler on the document was added before yours, and calls stopImmediatePropagation on the event. But this is rare.

See Bubbling and capturing explained for more background information.

answered Apr 12 '22 at 13:09

Thomas

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I will try it out – Apr 12 '22 at 13:15
It seems like changing the argument to `true` doesn't do anything – Apr 12 '22 at 13:18

score 0 · Accepted Answer · answered Apr 12 '22 at 13:12

0

If you can run your code before theirs, you can save the function

window.onmousemove = function()  {
  console.log("moving",new Date())
};
window.myMove = window.onmousemove;
document.getElementById("x").addEventListener("click",function() {
  window.onmousemove=null
})

document.getElementById("y").addEventListener("click",function() {
  window.onmousemove=myMove;
})

<button type="button" id="x">Turn off mousemove</button>
<button type="button" id="y">Turn mousemove back on</button>

answered Apr 12 '22 at 13:12

mplungjan

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And if my code comes after, It means I can't return `window.onmousemove` to its original value? – Apr 12 '22 at 13:14
This is the case. They turned `mousemove` to null. I've checked it in the console. How can I revert this? (If I can) – Apr 12 '22 at 13:23
Only by injecting before them – mplungjan Apr 12 '22 at 13:26
Is it possible with tampermonkey? – Apr 12 '22 at 13:30
https://stackoverflow.com/a/39347807/295783 – mplungjan Apr 12 '22 at 13:35

How to get over a blocked event?

2 Answers2