JSFiddle - React, Tailwind, and code Playground

HTML

<div class="prev-button"></div>
<div class="container">
    <div class="product"></div>
</div>

CSS

.prevButton {     
    border:1px solid green;    
}

/*note this class is not there in markup is added by jQuery*/

JavaScript

$(function () {
    $('.product').parent().siblings('.prev-button').addClass('prevButton');
})