Highlight active section link

active-section.js

$(document).ready(function () {
    var $sections = $(".content-item");
    var scrollFunc = function () {
        var scrollTop = $(this).scrollTop() + ((window.innerHeight || document.documentElement.clientHeight || document.body.clientHeight) / 3);

        var $activeSection = $($sections[0]);
        for (var i = $sections.length - 1; i >= 0; i--) {
            var $s = $($sections[i]);
            var divPosition = $s.offset().top;
            $activeSection = $s;
            if (scrollTop > divPosition) {
                console.info(i + ":" + divPosition + " < " + scrollTop);
                break;
            }
        }
        var id = $activeSection.find("h2").attr("id");
        $("a").removeClass("active");
        $('a[href="#' + id + '"]').addClass("active");
    };

    if ($sections) {
        scrollFunc();
        $(window).scroll(scrollFunc);
    }
});