Update HTMLMediaElement abort event description and example (#44222)

[vamshikrishnaramasamy]

The existing example on HTMLMediaElement: abort_event appends a <source> element to a <video>, which does not fire the abort event. Per @hamishwillee on #44222, abort is fired for user-intended cancellation of a media load — typically the browser's stop button, or changing/clearing src mid-load.

Changes:

• Description now states when the event fires, with the common triggers.
• Example replaced with one that actually fires abort: start loading a video, then change src to a different resource. Comment notes that clearing src or the browser's stop button have the same effect.

Closes #44222.

[github-actions]

Preview URLs (1 page)

• /en-US/docs/Web/API/HTMLMediaElement/abort_event

[chrisdavidmills]

@vamshikrishnaramasamy thanks for your contribution!

I tested this locally (in Chrome), and the code, as written, doesn't fire the abort event. It looks like the src replacement takes effect immediately, so it isn't seen as replacing the original src setting.

I did manage to get the event to fire with code like this:

const video = document.querySelector("video");

video.addEventListener("abort", () => {
  console.log("Video loading was aborted.");
});

video.setAttribute("src", "assets/bigbuckbunny.mp4");

setTimeout(() => {
  video.setAttribute("src", "");
}, 3000);

By the time the timeout ran, the video had completely loaded. This leads me to two bits of feedback concerning your work:

1. Test it more thoroughly, and make sure your code fires the event as advertised.
2. Think about your claim of "The abort event is fired when the loading of a media resource is canceled before it completes". Is it more generally when it is cancelled, but not as the result of an error?

[hamishwillee]

Is it more generally when it is cancelled, but not as the result of an error?

I seem to recall that is what the spec says - it should be " loading of a media resource is canceled by the user before it completes"

[hamishwillee]

@vamshikrishnaramasamy This issue was already taken by #44227 - you can see in the issue that they have a linked PR.

That issue was started first, so IMO the other one should continue and this should be closed
I've asked them to make sure that it is tested properly - learning from your work.

[vamshikrishnaramasamy]

Right on both counts. I didn't catch that setting src swaps in before abort can fire, and I missed that #44227 was already open against the same issue. Closing so the other PR can land. Thanks for testing it properly.