JSFiddle - React, Tailwind, and code Playground

JavaScript

function detect(URL) {
    var image = new Image();
    image.src = URL;
    image.onload = function() {
        var result = 'result'; // An example result
        alert(result); // Doesn't work
    }
    document.body.appendChild(image)
}

detect('http://www.roseindia.net/javascript/appendChild-1.gif');