javascript - How to detect CSS3 resize events

Question

The CSS3 resize property can be assigned to arbitrary elements. I'm looking for a way to detect such a resize on, say, divs (I don't mind it only working in Firefox at the moment):

div {
  resize: horizontal;
  overflow: hidden;
}

Unfortunately, the onresize event seems not to be fired on the div. How can I detect in JavaScript when such a user-instantiated resize has happened?

Edit: FWIW I had opened a bug report over at Mozilla. If you want to track it: https://bugzilla.mozilla.org/show_bug.cgi?id=701648

Answer 1

Resizing is like a style change. As such it can be observed with a MutationObserver.

let observer = new MutationObserver(function(mutations) {
  console.log('mutations:', mutations);
});

let child = document.querySelector('textarea');
observer.observe(child, { attributes: true });

<textarea></textarea>