jQuery實現判斷滾動條滾動到document底部的方法分析

//滾動條在Y軸上的滾動距離
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;
}
//文檔的總高度
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;
}
//瀏覽器視口的高度
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");
 }
});