DOMReady函数，只要DOM结构加载完成即可，不必等待所有资源加载完成，节约时间，"DOMContentLoaded"在H5中被标准化
var DOMReady=function(f,a,d){
d = d || document;
a = a || "addEventListener";
d[a]?d[a](‘DOMContentLoaded‘,f,false):window.attachEvent(‘onload‘,f);
}
DOMReady(function(){
alert("The DOM is Ready");
})
检查元素是否在视窗（分完全在视窗内，部分在视窗内以及完全不在视窗内）
function isInViewPort(ele){
var rect=ele.getBoundingClientRect();
alert(rect.top+","+rect.right+","+rect.bottom+","+rect.left);
var newRect=getRect(ele);
alert(newRect.top+","+newRect.right+","+newRect.bottom+","+newRect.left);
return rect.top < (window.innerHeight || document.documentElement.clientHeight) &&
rect.right < (window.innerWidth || document.documentElement.clientWidth) &&
rect.bottom < (window.innerHeight || document.documentElement.clientHeight) &&
rect.left < (window.innerWidth || document.documentElement.clientWidth);
}
IE7及以下浏览器的坐标从（2,2）开始计算，需要提供兼容方案
function getRect(ele){
var rect=ele.getBoundingClientRect();
var top=document.documentElement.clientTop; //IE=2 非IE=0
var left=document.documentElement.clientLeft; //IE=2 非IE=0
return{
top:rect.top-top,
bottom:rect.bottom-top,
left:rect.left-left,
right:rect.right-left
}
}
原文：http://www.cnblogs.com/diantao/p/4937411.html