JSFiddle - React, Tailwind, and code Playground

HTML

<div id="first_container">
This is the first container
</div>

CSS

#first_container.myClass1 { background-color: red; }
#first_container.myClass2 { background-color: green; }
#first_container.myClass3 { background-color: blue; }

JavaScript

$(function () {
	var randomClass = "myClass".concat(Math.floor(Math.random() * 3) + 1);
	$('#first_container').addClass(randomClass);
})();