JSFiddle - React, Tailwind, and code Playground

HTML

<ul id="stack">
  <li></li>
  <li></li>
  <li></li>
  <li></li>
  <li></li>
</ul>

JavaScript

$(document).ready(function() {
	$('#stack li').each(function(index) {
  	$(this).addClass('item' + ++index);
  })
});