问将导航定位固定在顶部，然后在车身上增加边距。

EN

    $(function(){ // document ready

      var stickyTop = $('.navigation-wrap').offset().top; // returns number 

      $(window).scroll(function(){ // scroll event  
        var windowTop = $(window).scrollTop(); // returns number
        if (stickyTop < windowTop) {
          $('.navigation-wrap').addClass('sticky');
        }
        else {
          $('.navigation-wrap').removeClass('sticky');
        }
      });

    });

$(document).ready(function () {
    $(document).on("scroll", onScroll);

    //smoothscroll
    $('a[href^="#"]').on('click', function (e) {
        e.preventDefault();
        $(document).off("scroll");

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

        var target = this.hash,
            menu = target;
        $target = $(target);
        $('html, body').stop().animate({
            'scrollTop': $target.offset().top+2
        }, 500, 'swing', function () {
            window.location.hash = target;
            $(document).on("scroll", onScroll);
        });
    });
});