JSFiddle - React, Tailwind, and code Playground

HTML

<div id="w">abc</div>

<input id="b" type="button" value="change html" />

JavaScript

var div = document.getElementById("w");

var w1 = { watch: null, prev: div.innerHTML };

function Watch(w, e)
{
    w.watch = setInterval(function() {
       if (e.innerHTML != w.prev)
       {
           w.prev = e.innerHTML;
           alert("changed");
       }
    }, 100);
}

Watch(w1, div);

document.getElementById("b").onclick = function() {
     document.getElementById("w").innerHTML = Math.random();
};