Simple scrollspy

NSA Navigation

var lastId,
    topMenu = $("#Navigation"),
    topMenuHeight = topMenu.outerHeight()+0,
    menuItems = topMenu.find("a"),
    scrollItems = menuItems.map(function(){
      var item = $($(this).attr("href"));
      if (item.length) { return item; }
    });

menuItems.click(function(e){
    var href = $(this).attr("href"),
        offsetTop = href === "#" ? 0 : $(href).offset().top-topMenuHeight+1;
    $('html, body').stop().animate({ 
        scrollTop: offsetTop
    }, 600);
    e.preventDefault();
});

function highlightNav() {
   var fromTop = $(window).scrollTop()+topMenuHeight;
   var cur = scrollItems.map(function(){ if ($(this).offset().top < fromTop) { return this; } });
   cur = cur[cur.length-1];
   var id = cur && cur.length ? cur[0].id : "";
   console.log("id",id);
   if (lastId !== id) {
       lastId = id;
       // Set/remove active class
       menuItems
         .removeClass("is-Current")
         .filter("[href=#"+id+"]").addClass("is-Current");
   }   
}
highlightNav();
$(window).scroll( highlightNav );