JSFiddle - React, Tailwind, and code Playground

HTML

<h2>Unordered List</h2>
    <ul>
        <li>First list item</li>
        <li>Second list item</li>
        <li>Third list item</li>
        <li>Fourth list item</li>
    </ul>
	<hr>
  
	<h2>Another Unordered List</h2>
	<ul>
        <li>First list item</li>
        <li>Second list item</li>
        <li>Third list item</li>
        <li>Fourth list item</li>
   </ul>

CSS

.eq{
        background: yellow;
}
.nth{
        background: red;
}

JavaScript

$("li:nth-child(2)").addClass("nth");
$("li:eq(2), li:eq(6)").addClass("eq");