JSFiddle - React, Tailwind, and code Playground

HTML

<div></div>

CSS

div {
    position: absolute;
    width: 100px;
    height: 100px;
    background-color: black;
    opacity: 0;
    transition: opacity 1000ms linear;
}
.foo {
    opacity: 1;
}

JavaScript

$('div').addClass('foo');