JSFiddle - React, Tailwind, and code Playground

HTML

<body>
    <div id="background">.
    </div>
    <p>hello world</p>
    <p>hello world</p>
    <p>hello world</p>
    <p>hello world</p>    
</body>

CSS

#background {
    background-image: url("http://media.noupe.com//uploads/2009/10/wallpaper-pattern.jpg");
    opacity: 0;
    margin: 0;
    padding: 0;
    z-index: -1;
    position: absolute;
    width: 100%;
    height: 100%;
}

JavaScript

$(document).ready(function(){
    $('#background').animate({ opacity: 1 }, 3000);
});