jQuery实现判断滚动条滚动到document底部的方法分析

//滚动条在Y轴上的滚动距离
function getScrollTop() {
    var scrollTop = 0,
      bodyScrollTop = 0,
      documentScrollTop = 0;
    //兼容谷歌
    if (document.body) {     bodyScrollTop = document.body.scrollTop;   }
    //兼容火狐
    if (document.documentElement) {     documentScrollTop = document.documentElement.scrollTop;   }
       scrollTop = (bodyScrollTop - documentScrollTop > 0) "you are in the bottom!");
    }
};

$(window).scroll(function(){
  var scrollTop = $(this).scrollTop();
  var scrollHeight = $(document).height();
  var windowHeight = $(this).height();
  if(scrollTop + windowHeight == scrollHeight){
    alert("you are in the bottom");
  }
});