JSFiddle - React, Tailwind, and code Playground

HTML

<ul class="list">
    <li>1</li>
	<li class="foo">2</li>
	<li class="foo">3</li>
	<li class="foo">4</li>
	<li>5</li>
</ul>

CSS

.someClass {
  color: red;
}

JavaScript

var $lis = $("ul.list li.foo");
$lis.first().addClass("someClass");
$lis.last().addClass("someClass");