please help, why isn't this function working? : I have been trying to get this simple function to work by using this callback but I don't understand what I am doing wrong. I want to invoke a function when the scrolltop is greater than zero. I am new to programming - it might seem like a stupid question but I can't figure it out. 
Is it a formatting issue?

        function alertme() {
        var $window = $(window);
        var window_top = $window.scrollTop(0);
        if (window_top > 0) {
        alert("alertme");
        };
        };