javascript - 根据滚动位置更新选择菜单中的选定选项

Question

我有一种单页网站，它使用标准的 ul 菜单作为导航，然后在移动设备上使用选择菜单。我已经整理出如何根据可见/滚动到 div 设置“事件”菜单项，但我不确定如何更改事件选项以达到相同的效果。我在这里设置了一个 fiddle ，供您查看到目前为止我在哪里。代码也在下面

http://jsfiddle.net/e9XG5/3/

    // This function will be executed when the user scrolls the page.
    $(window).scroll(function(e) {
    // Get the position of the location where the scroller starts.
    var scroller_anchor = $(".scroller_anchor").offset().top;

    // Check if the user has scrolled and the current position is after the scroller's start location and if its not already fixed at the top 
    if ($(this).scrollTop() >= scroller_anchor && $('.scroller').css('position') != 'fixed') 
    {    // Change the CSS of the scroller to hilight it and fix it at the top of the screen.
        $('.scroller').addClass('sloozis');
        // Changing the height of the scroller anchor to that of scroller so that there is no change in the overall height of the page.
        $('.scroller_anchor').css('height', '50px');
    } 
    else if ($(this).scrollTop() < scroller_anchor && $('.scroller').css('position') != 'relative') 
    {    // If the user has scrolled back to the location above the scroller anchor place it back into the content.

        // Change the height of the scroller anchor to 0 and now we will be adding the scroller back to the content.
        $('.scroller_anchor').css('height', '0px');

        // Change the CSS and put it back to its original position.
        $('.scroller').removeClass('sloozis');
    }
    var lastId,
    topMenu = $(".nav"),
    topMenuHeight = topMenu.outerHeight()+15,
    // All list items
    menuItems = topMenu.find("a"),
    // Anchors corresponding to menu items
    scrollItems = menuItems.map(function(){
      var item = $($(this).attr("href"));
      if (item.length) { return item; }
    });

   // Get container scroll position
   var fromTop = $(this).scrollTop()+topMenuHeight;

   // Get id of current scroll item
   var cur = scrollItems.map(function(){
     if ($(this).offset().top < fromTop)
       return this;
   });
   // Get the id of the current element
   cur = cur[cur.length-1];
   var id = cur && cur.length ? cur[0].id : "";

   if (lastId !== id) {
       lastId = id;
       // Set/remove active class
       menuItems
         .parent().removeClass("active")
         .end().filter("[href=#"+id+"]").parent().addClass("active");
   }                   
});

 $(document).ready(function(e) {

        $('#nav ul li a').bind('click', function(e) {
            e.preventDefault();
            $('html,body').animate({scrollTop: $(this.hash).offset().top});                                                         
        });     
         });

Answer 1

修复:http://jsfiddle.net/x3MLa/

您没有更新所选选项，将类似这样的内容添加到您更新 anchor 的位置:

if (lastId !== id) {
    lastId = id;
    // Set/remove active class
    menuItems.parent().removeClass("active")
        .end().filter("[href=#" + id + "]").parent().addClass("active");

    //added to update the correct option in the dropdown menu
    $('option[value="#' + id + '"]').attr('selected','selected');
}