Навигация с активным пунктом при скролле

html + javascript

    <ul class="navigation clearfix">

        <li>
            <a href="#block1" class="navigation_item current">Scroll block 1</a>
        </li>

        <li>
            <a href="#block2" class="navigation_item">Scroll block 2</a>
        </li>

        <li>
            <a href="#block3" class="navigation_item">Scroll block 3</a>
        </li>

        <li>
            <a href="#block4" class="navigation_item">Scroll block 4</a>
        </li>

    </ul>

    <div id="block1" class="section">Scroll block 1</div>
    <div id="block2" class="section">Scroll block 2</div>
    <div id="block3" class="section">Scroll block 3</div>
    <div id="block4" class="section">Scroll block 4</div>

    self.navigation.init();

    /**
    **  Main navigation
    **/

    navigation: {

        init: function () {

            var self = this;

            self.w = $(window);
            self.body = $('body');
            self.nav = $('.wrapp_header.pos_absolute');
            self.section = $('.section');
            self.sectionQt = self.section.length;

            self.anchorScroll();

            self.openCloseMenu();

            self.w.on('scroll',function(){

                self.pageScroll();
                self.sticky();

            });
            // sticky
            self.header = $('.wrapp_header.pos_absolute');

            self.sticky();

            self.w.on('resize',function(){

                self.sticky();

            });

        },

        anchorScroll: function(){

            var self = this;

            self.nav.on('click', ".navigation_item", function(event){

                event.preventDefault();

                var $this = $(this),
                    item = $this.parent(),
                    dataId = $this.attr('href'),
                    offset = $(dataId).offset().top;


                $this.addClass('current').parent().siblings().find('a').removeClass('current');

                self.scrollContent(offset);

            });

        },

        scrollContent: function(offset){

            var self = this;

            self.body.addClass('scrollContent');

            $('html,body').stop().animate({

                scrollTop: offset

            },1200,function(){

                self.body.removeClass('scrollContent');

            });

        },

        pageScroll: function(){

            var self = this;

            if(self.body.hasClass('scrollContent'))return;

            self.wScroll = self.w.scrollTop();
            self.wHeightHalf = self.w.height()/2;

            for (var i = 0; i <= self.sectionQt - 1; i++) {

                var offset = $(self.section[i]).offset().top,
                    heightBox = $(self.section[i]).outerHeight(),
                    bottomOffset = $(self.section[i+1]).length ? $(self.section[i+1]).offset().top : offset + heightBox,
                    id = $(self.section[i]).attr('id'),
                    activItem = $('.wrapp_header.pos_absolute').find("a[href='" + "#" + id + "']");

                if(self.wScroll + self.wHeightHalf > offset && self.wScroll + self.wHeightHalf < bottomOffset ){

                    activItem.addClass('current').parent().siblings().find('a').removeClass('current');

                    return false;

                }

            };

        },

        sticky: function(){

            var self = this;

            self.wHeight = self.w.height();
            self.wScroll = self.w.scrollTop();
            self.headerHeight = self.header.outerHeight();

            if(self.wScroll <= self.headerHeight){

                if(self.position == 'top') return false;

                self.position = 'top';
                self.header.removeClass('sticky').stop().animate({
                    "top": 0
                },0);

            }
            else if(self.wScroll > self.headerHeight && self.wScroll < self.wHeight/1.5){

                if(self.position == 'hide') return false;

                if(self.position == 'top'){

                    self.position = 'hide';
                    self.header.addClass('sticky').stop().animate({
                        'top': -self.headerHeight
                    },0);

                }
                else{

                    self.position = 'hide';
                    self.header.stop().animate({
                        'top': -self.headerHeight
                    },300, function(){
                        self.header.addClass('sticky');
                    });

                }

            }
            else{

                if(self.position == 'sticky') return false;

                self.position = 'sticky';
                self.header.addClass('sticky');
                self.header.stop().animate({
                    'top': 0
                });

            }

        },

        openCloseMenu: function() {

            $(".nav_btn").on("click", function () {

                $(this).toggleClass("active").stop();

                $(".navigation").toggleClass("open").stop();


            });

        },

    },