JSFiddle - React, Tailwind, and code Playground

HTML

<div class="outer">

<div class="foo bar"></div>

</div>

<div clas="bar"></div>

CSS

div {
    border: 1px solid #ccc;   
    width: 10px;
    height: 10px;
}

JavaScript

$('.outer:has(.bar)').css('border', '1px solid #f00');