JSFiddle - React, Tailwind, and code Playground

by mvasilkov

HTML

<div id="a"></div>

<div id="b"></div>

CSS

#a {
    width: 100px;
    height: 100px;
    background: red;
    opacity: 0;
    
    transition: opacity 1s;
}

#a.x { opacity: 1 }


#b {
    margin-top: 20px;
    width: 0;
    height: 0;
    border-width: 0 20px 40px;
    border-style: solid;
    border-color: transparent transparent  green;
}

JavaScript

$('#a').addClass('x')