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) ? bodyScrollTop : documentScrollTop;    return scrollTop;}//文档的总高度function getScrollHeight() {    var scrollHeight = 0,      bodyScrollHeight = 0,      documentScrollHeight = 0;    //兼容谷歌    if (document.body) {      bodyScrollHeight = document.body.scrollHeight;    }    //兼容火狐    if (document.documentElement) {      documentScrollHeight = document.documentElement.scrollHeight;    }    scrollHeight = (bodyScrollHeight - documentScrollHeight > 0) ? bodyScrollHeight : documentScrollHeight;    return scrollHeight;}//浏览器视口的高度function getWindowHeight() {    var windowHeight = 0;    windowHeight = document.documentElement.clientHeight;    return windowHeight;}window.onscroll = function() {    if (getScrollTop() + getWindowHeight() == getScrollHeight()) {      alert("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");  }});