JSFiddle - React, Tailwind, and code Playground

HTML

<script src="http://ajax.microsoft.com/ajax/jquery.validate/1.7/jquery.validate.js"></script>
<link rel="stylesheet" href="http://ajax.googleapis.com/ajax/libs/jqueryui/1.8.4/themes/ui-lightness/jquery-ui.css">
<div class='class1'></div>

CSS

div {
    width: 100px;
    height: 100px;
}
.class1 {background-color:blue;}
.class2 {background-color:red;}

JavaScript

setTimeout(function() {
    $('div').addClass('class2', 1000);
}, 1000);