JSFiddle - React, Tailwind, and code Playground

HTML

<ul>
    <li class="box">a</li>
    <li class="box">b</li>
    <li class="box">c</li>
    <li class="box">d</li>
  </ul>

CSS

li {
  height:20px;
  width:20px;
  background-color:red;
  display:inline-block;
}

li .hover {
  background-color:blue;
}

JavaScript

$('li').addClass('hover');