jQuery scroller, like bootstrap scrollspy

gistfile1.js

$(document).ready(function(){
	var lastId, topMenu = $("#navbar-scroll"),
	    topMenuHeight = topMenu.outerHeight() + 150,
	    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"),
	    topMenuHeight = topMenu.outerHeight() + 20,
	        offsetTop = href === "#" ? 0 : $(href).offset().top - topMenuHeight + 1;
	    $('html, body').stop().animate({
	        scrollTop: offsetTop
	    }, 300);
	    e.preventDefault();
	});

	$(window).scroll(function() {
	    var fromTop = $(this).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 : "";

	    if (lastId !== id) {
	        lastId = id;
	        menuItems.parent().removeClass("active").end().filter("[href=#" + id + "]").parent().addClass("active");
	    }
	});
});