JSFiddle - React, Tailwind, and code Playground

HTML

<script src="http://ajax.googleapis.com/ajax/libs/jqueryui/1.8/jquery-ui.min.js"></script>
<div id="frame">
    <div id = "block1" class="">test</div>
</div>

CSS

#block1 {
    
 background-color:red; 
 width:100px;
}

#frame.on #block1 {
    width:400px;
}

JavaScript

$("#frame").delay(1000).addClass("on", 1000);