向下滚动隐藏副标题，向上滚动显示

Question

我有一个子标题，默认情况下必须是静态的，在向下滚动时隐藏，并在向上滚动时显示为固定。有一个fiddle。我试图混合一个类别的Bootstrap和这个sample，但它不起作用。 我的js代码：

// Hide Header on on scroll down
var didScroll;
var lastScrollTop = 0;
var delta = 5;
var navbarHeight = $('.header2').outerHeight();

$(window).scroll(function(event){
    didScroll = true;
});

setInterval(function() {
    if (didScroll) {
        hasScrolled();
        didScroll = false;
    }
}, 250);

function hasScrolled() {
    var st = $(this).scrollTop();

    // Make sure they scroll more than delta
    if(Math.abs(lastScrollTop - st) <= delta)
        return;

    // If they scrolled down and are past the navbar, add class .nav-up.
    // This is necessary so you never see what is "behind" the navbar.
    if (st > lastScrollTop && st > navbarHeight){
        // Scroll Down
        $('header').addClass('nav-up');
    } else {
        // Scroll Up
        if(st + $(window).height() < $(document).height()) {
            $('header').removeClass('nav-up');
        }
    }

    lastScrollTop = st;
}

$('#sticky').affix({
    offset: {
        top: 60
    }
});