Question

I need just one callback at the and of multiple callbacks. With a simple “class” MultiCallback that count the calls it seems to be solved.
But the fadeIn function of jQuery calls mCallback just once.

It have to call mCallback 3 times. That happens by using a callback function directly inside top scope.

Tested my MultiCallback class also on my own functions without any problems. I know
there a other ways like Hide multiple elements with jQuery and get one callback…
Just wanna know what is wrong with my logic.

<div id="1" style="display: none; background-color: green;"></div>
<div id="2" style="display: none; background-color: red;"></div>
<div id="3" style="display: none; background-color: blue;"></div>

<script>

    var allElements = "#1, #2, #3";
    var multiCallback = new MultiCallback( $(allElements).length, function()
            {
                console.log("NEVER ENTER CALLBACK");
            });
    $(allElements).fadeIn(400, multiCallback.mCallback());

    function MultiCallback(limit, fn)
    {
        var finishedCalls = 0;

        function mCallback()
        {
            // Just enter one time !
            if (++finishedCalls == limit)
            {
                fn();
            }
        }

        return {
            mCallback : mCallback
        }
    }

</script>

Answer 1

Change

// executes function, returns undefined, passing undefined
$(allElements).fadeIn(400, multiCallback.mCallback());

to

// pass a reference to the function
$(allElements).fadeIn(400, multiCallback.mCallback);