Function inside jquery returns undefined [duplicate]

Answer 1

The function addToPlaylist doesn't return anything. It makes an asynchronous request, which eventually executes a callback function, which returns something. The original addToPlaylist function is long done and returned by the time this happens though, and the callback function returns to nobody.

I.e. the success: function(msg) { } code executes in a different context and at a later time than the surrounding addToPlaylist function.

Try this to see it in action:

function addToPlaylist() {
    $.ajax({
        ...
        success : function () {
            alert('second');  // comes after 'first'
            return null;      // returns to nobody in particular
        }
    });
    alert('first');      // comes before 'second'
    return 'something';  // can only return here to caller
}