scrolling.js

/**
 * Для плавного перехода по ссылкам
 */
$(document).ready(function () {
    $('.panel-nav a[href="#about-us"]').addClass('active');
    $(document).on("scroll", onScroll);
    //smoothscroll
    $('.panel-nav a[href^="#"]').on('click', function (e) {
        e.preventDefault();
        $(document).off("scroll");

        $('a').each(function () {
            $(this).removeClass('active');
        })
        $(this).addClass('active');

        var target = this.hash,
            menu = target;
        $target = $(target);
        $('html, body').stop().animate({
            'scrollTop': $target.offset().top - 95
        }, 1000, 'swing', function () {
            window.location.hash = target;
            $(document).on("scroll", onScroll);
        });
    });
});

function onScroll(event) {
    var scrollPos = $(document).scrollTop();
    if ($(window).scrollTop() + $(window).height() == $(document).height()) {
        $('.panel-nav a').each(function () {
            $(this).removeClass("active");
        });
        $('.panel-nav a[href="#support"]').addClass('active');
    } else {
        $('.panel-nav a').each(function () {
            var currLink = $(this);
            var refElement = $(currLink.attr("href"));
            if (refElement.position().top - 95 <= scrollPos && refElement.position().top + refElement.height() > scrollPos) {
                $('.panel-nav ul li a').removeClass("active");
                currLink.addClass("active");
            } else {
                currLink.removeClass("active");
            }
        });
    }
}