JSFiddle - React, Tailwind, and code Playground

HTML

<div id="div1">

</div>

CSS

#div1 {
  width: 30px;
  height: 30px;
  background: #ff0000;
}

#div1.classAdded {
  background: #AA8888;
}

JavaScript

jQuery(document).ready(function($) {
	$('#div1').addClass('classAdded');
  $('body').addClass('scrollbar-dynamic');
});