JSFiddle - React, Tailwind, and code Playground

HTML

<div id="test"></div>

CSS

#test { height: 100px; width: 100px; background: #000; }

JavaScript

var block = $("#test");
block
   .css({ opacity: 0.3 })
   .animate({ opacity: 1 }, 2000, incre);
function incre() { alert('complete'); }