JSFiddle - React, Tailwind, and code Playground

HTML

<div class="list-group" id="setActive">
    <a href="#">aaa</a>
    <a href="#">bbb</a>
    <a href="#">ccc</a>
</div>

CSS

.list-item {
    color: red;
}

JavaScript

$(document).ready(function() {

    var setActive = document.getElementById('setActive'),
        anchor = setActive.getElementsByTagName('a');

    for (i = 0; i < anchor.length; i++) {
        anchor[i].className = "list-item";
    }
    
 });