Add and Remove Class on Menu Item on Scroll

<script>
	jQuery(function (jQuery) {
	   // jQuery('#menu:first-child li').addClass('xx-menu-active');
	    jQuery(window).scroll(function () {
	        var scrollPos = jQuery(window).scrollTop();
	        jQuery('.xx-section').each(function (i) {
	            var topPos = jQuery(this).offset().top;
	            if ((topPos - scrollPos) <= 180) {
	                jQuery('.xx-menu-active').removeClass('xx-menu-active')
	                jQuery('#menu li').eq(i).addClass('xx-menu-active')
	            }
	        })
	    });
	});
</script>

This code will add or remove a CSS class on a menu item that is an anchor link. To be used on a single page navigation menu. Each section needs to be given the class .xx-section.