JSFiddle - React, Tailwind, and code Playground

by Pointy

HTML

<div id='x'></div>

JavaScript

function hasWebP() {
    var rv = $.Deferred(), img = new Image();
    img.onload = function() { rv.resolve(); };
    img.onerror = function() { rv.reject(); };
    img.src = "http://www.gstatic.com/webp/gallery/1.webp";
    return rv.promise();
}

hasWebP().then(function() {
    $('#x').text("Hooray!!  WebP is enabled.  Things will be wonderful now.");
}, function() {
    $('#x').text("Note: your browser does not support the new Google WebP format. Please remain where you are while our support team locates you to begin the reeducation process.");
});