// Hide Header on on scroll down 
var didScroll; 
var lastScrollTop = 0; 
var delta = 5; 
var navbarHeight = $('#menuNav').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 
        $('#menuNav').removeClass('line_up').addClass('line_down'); 
    } else { 
        // Scroll Up 
        if(st + $(window).height() < $(document).height()) {
         $('#menuNav').removeClass('line_down').addClass('line_up'); 
        } 
    } 
    
    lastScrollTop = st; 
}