JSFiddle - React, Tailwind, and code Playground

HTML

<div id="mutable" style="width:50px;height:50px;">sjdfhksfh<div>
<div>
  <button id="changeClass">Change Class</button>
</div>

CSS

.red{
    background-color:red;
}

JavaScript

$(document).ready(function() {
  $('#changeClass').click(function() {
    $('#mutable').addClass("red");
  });
  
  $('#mutable').bind('DOMSubtreeModified', function(e) {
      alert('class changed');
  });
});