JSFiddle - React, Tailwind, and code Playground

HTML

<div id="test1" class="test">
    <div id="test2">
    Hello
    </div>    
 </div>

CSS

.test {
    border: 1px solid;
    cursor: pointer;
    height: 10px;
    position: relative;
    width: 100%;
    display:none;
}

#test2{
    width:100%;
}

JavaScript

alert($('#test2').width());