JSFiddle - React, Tailwind, and code Playground
HTML
<div id="block"></div>
CSS
#block {width:100px;height:100px;background:green;}
JavaScript
Number.prototype.round = function(n){ return parseFloat(this.toFixed(n)) }
Object.prototype.isInt = function(){ return this instanceof Number && /^\d+$/.test(this.toString()) }
$(document).ready(function()
{
// alert((3).isInt());
$("#block").css("background","red")
$("#block").slideUp();
})