JSFiddle - React, Tailwind, and code Playground

HTML

<div class='container'>
    <div class='item'></div>
</div>

CSS

.container{
    width:200px;
    height:500px;
    background-color:red;
}
.item{
    width:100px;
    height:250px;
    background-color:yellow;
    
}

JavaScript

$('.item').width($('.container').width());