scrollSpy.js

jQuery(function(){
    var items = [];
var key  = 0;
var nav  = jQuery(".itens-topo a");

	nav.each(function(){
		
		var target  = jQuery(this).attr('href');
		var section =  jQuery(target);
		if(section.length) {
			var topSection      = section.offset().top;
			var heightSection       =  topSection + section.height();
			items.push({id : target, start: topSection, end :  heightSection, index : key});		
		}
		key++;
});

jQuery(window).scroll(function(){
	var currentScroll = jQuery(document).scrollTop();
	items.forEach(function(item){
		 if(item.start <= currentScroll && item.end > currentScroll) {
			 nav.removeClass('active')
		     nav.eq(item.index).addClass('active');
		 }
	});
});
});