javascript代码片段

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
	}
}