JSFiddle - React, Tailwind, and code Playground

HTML

<div id=aDiv></div>
Resize this DIV with your mouse.<br>
Google Chrome console won't show any massage.

CSS

#aDiv {background: gray ; resize: both ; overflow: auto ; width: 200px ; height: 200px}

JavaScript

$(function(){
    
mutObs = new MutationObserver(function(){
	console.log('Hello') ;
}) ;
elem = document.getElementById('aDiv') ;
mutObs.observe(elem,{attributes:true}) ;
elem.style.width = '300px' ; //this fires the observer callback as expected

}) ;