JSFiddle - React, Tailwind, and code Playground

HTML

<div class="defaultblock">
    <div class="blockcontent">
        <div id="group-id-tids-11" class="advertisement" >
            Inner content
        </div>
    </div>
</div>

CSS

.test{
    background-color:red,
}

JavaScript

$(".blockcontent .advertisement").parent().addClass(test);
//You would put in .css({border: "3px"})   I made the background red, so you could see the change...