Question

I have a JS function where a value is computed and this value should be returned but I get everytime undefined but if I console.log() the result within this function it works. Could you help?

function detect(URL) {
    var image = new Image();
    image.src = URL;
    image.onload = function() {
        var result = [{ x: 45, y: 56 }]; // An example result
        return result; // Doesn't work
    }
}

alert(detect('image.png'));

Answer 1

I get it myself:

I didn’t know that I can assign a variable to that (for me looking already assigned) onload.

function detect(URL) {
    var image = new Image();
    image.src = URL;
    var x = image.onload = function() {
        var result = [{ x: 45, y: 56 }]; // An example result
        return result;
    }();
    return x;
}

alert(detect('x'));