js控制html页面滚动条到底端触发事件

 //文档高度

function getDocumentTop() {

var scrollTop = 0, bodyScrollTop = 0, documentScrollTop = 0;

if (document.body) {

   bodyScrollTop = document.body.scrollTop;

}

if (document.documentElement) {

   documentScrollTop = document.documentElement.scrollTop;

}

scrollTop = (bodyScrollTop - documentScrollTop > 0) ? bodyScrollTop : documentScrollTop;    return scrollTop;

}

//可视窗口高度

function getWindowHeight() {

var windowHeight = 0;    if (document.compatMode == "CSS1Compat") {

   windowHeight = document.documentElement.clientHeight;

} else {

   windowHeight = document.body.clientHeight;

}

return windowHeight;

}

//滚动条滚动高度

function getScrollHeight() {

var scrollHeight = 0, bodyScrollHeight = 0, documentScrollHeight = 0;

if (document.body) {

   bodyScrollHeight = document.body.scrollHeight;

}

if (document.documentElement) {

   documentScrollHeight = document.documentElement.scrollHeight;

}

scrollHeight = (bodyScrollHeight - documentScrollHeight > 0) ? bodyScrollHeight : documentScrollHeight;    

return scrollHeight;

}

window.onscroll = function () {

//监听事件内容

if(getScrollHeight() == getWindowHeight() + getDocumentTop()){

    //当滚动条到底时,这里是触发内容

    //异步请求数据,局部刷新dom
            ajax_function() 

}

}