<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"
"http://www.w3.org/TR/html4/loose.dtd">
<html>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<head>
<title>getElementByClassName封装用法</title>
<script type="text/javascript">
function $(node){
node=typeof node=="string"?document.getElementById(node):node;
return node;
}
function getClassName(str,root,tag){
if(root){
root=typeof root=="string"?document.getElementById(root):root;
}else{
root=document.body;
}
tag=tag||"*";
var els=root.getElementsByTagName(tag),arr=[];
for(var i= 0,n=els.length;i<n;i++){
for(var j= 0,k=els[i].className.split(" "),l= k.length;j<l;j++){
if(k[j]==str){
arr.push(els[i]);
break;
}
}
}
return arr;
}
window.onload=function(){
var a=getClassName("a");
var b=getClassName("b",null,"strong");
var c=$("box");
var d=getClassName("b",c);
for(var i=0;i< a.length;i++){
a[i].onclick=function(){
alert(this.innerHTML);
}
}
//alert(a.length);
//alert(b.length);
//alert(d.innerHTML);
alert(d.length);
}
</script>
</head>
<body>
<span class="a">aa</span>
<span class="a">aa2</span>
<p class="a">aaa333</p>
<strong class="b">bbbb</strong>
<div id="box"><strong class="b">sdfdsf</strong></div>
</body>
</html>
getClassName函数接收三个参数，其中第一个参数是必选的，后面两个参数可选。第一个参数是class名，第二个参数是父容器，缺省为body节点，第三个参数为DOM节点的标签名