Turn an image's onError function into a return

Question

So I need a function to test if an image can load or not. Here's what I've got:

function imgExists(url){
    var img = new Image();
    img.onerror = function(){
        alert('error')
    }
    img.onload = function (){
    alert('load')
    }
    img.src = url;
}

imgExists('http://hashtraffic.com/img/jackson@2x.png')

The issue is that the alerts are trapped in their won functions. How can I get the imgExists() function to return true if the image loads and false if it does not?

Answer 1

You need to use a callback, since your function is inherently asynchronous:

function imgExists(url, callback) {
    var img = new Image();
    img.onerror = function() {
        callback(false);
    }
    img.onload = function () {
        callback(true);
    }
    img.src = url;
}

function checkImage(exists) {
    alert("Image exists: " + exists); // Usage example.
}

imgExists('http://hashtraffic.com/img/jackson@2x.png', checkImage);