JSFiddle - React, Tailwind, and code Playground

by Jon Lambell

HTML

<span id="test">Content</span>

<div id="overlay" class="overlay"></div>

CSS

.overlay {
    width:100%;
    height:100%;
    position: absolute;
    z-index:1000;
    background-color:rgba(255, 255, 255, 0.8);
    color:#000;
    visibility: hidden;
    left: 0;
    top: 0;
    text-align: center;
    background-image: url('http://pic2.pbsrc.com/common/loading.gif');
    background-position: center;
    background-repeat: no-repeat;
}

JavaScript

window.onbeforeunload = function () {
    document.getElementById("overlay").style.visibility = 'visible';
};