var $window = $(window),
    lastScrollTop = 0;

function onScroll (e) {
    var top = $window.scrollTop();
    if (lastScrollTop > top) {
        console.log('top');
    } else if (lastScrollTop < top) {
        console.log('down');
    }
    lastScrollTop = top;
}

$window.on('scroll', onScroll);