$(window).scroll(function () {
      var scrollTop = $(this).scrollTop();
      var scrollHeight = $(document).height();
      var windowHeight = $(this).height();


      if (scrollTop + windowHeight >= scrollHeight) {
        loadPromotions();
      }

    });

   var page = 1;
   var morAvaliable = true;//标识还有数据可以加载
   function loadPromotions() {
    if (morAvaliable) {
      var href = location.href.split('"task-time">' + list.CreateTime + '</div>';
              html += '<a class="task-box" href="' + list.Url + '">';
              html += '<h5>' + list.Title + '</h5>';
            });
            $('#promotionList').append(html);
          }
          else {
            morAvaliable = false;
            $('#loading').html('没有更多分享信息了');
          }
        }
      );
    }
  }