<!doctype html>

 <html>

 <head>

 <meta charset="utf-8">

 <meta name="author" content="前端工程师——和派孔明" />

 <meta name="copyright" content="前端工程师——和派孔明" />

 <title>getElementsByClassName IE低不兼容解决</title>

 <style>

 * {

margin: 0;

padding: 0;

list-style: none;

font-family: "微软雅黑", "张海山锐线体简"

 }

 div {

height: 50px;

background: #ccc;

margin: 10px;

 }

 </style>

 <script>

 window.οnlοad=function(){

var aBox = getByClass(document,'box');


for(var i=0;i<aBox.length;i++){

aBox[i].style.background='red';
 

}

 };



function getByClass(oParent,sClass){
var aEle = oParent.getElementsByTagName('*');//父级获取下面所有
var result=[];//准备空数组
for(var i=0;i<aEle.length;i++){
//临时数组,装切出来的单个aEle 元素的class
var tmpArr = aEle[i].className.split(' ');//[box a b c d e f g]
for(var j=0;j<tmpArr.length;j++){
if(tmpArr[j] == sClass){//数组里每一个字符和传入的box对比
result.push(aEle[i]); 
break;
}
}
} 
return result;
 }

 </script>

 </head>



 <body>



     <div class="box a b c d e f g">box a b c d e f g</div>

     <div class="">空</div>

     <p class="active box">active box</p>

     <div>空</div>

     <div class="a_box_b">a_box_b</div>

 </body>

 </html>