DOM已经实现了getElementByClass，这个功能内部是怎么实现的呢
js代码及如何使用：
function getElementByClass(className,parentNode){
parentNode = parentNode || document;
var childrens = parentNode.getElementsByTagName(‘*‘);
var nodeArr = [];
for(var i=0;i<childrens.length;i++){
if(childrens[i].className == className){
nodeArr.push(childrens[i]);
}
}
return nodeArr;
}
var parentNode = document.getElementById(‘target‘);
var classNode = getElementByClass("pullright");
console.log(classNode);
html代码：
<div class="container" id="target"> <div class="pullleft"> <span>这里是左浮动</span> </div> <div class="pullright"> <span class="pullleft">这里是右浮动内容</span> </div> <p class="pullleft">这里是需要浮动的文本</p> </div>
原文：http://www.cnblogs.com/diantao/p/5215734.html