DOM子节点比较问题?
<html>  
  <head>  <title> Test </title>  
  <script   type= "text/javascript ">  
 function   nodecheck(parentNode,childNode) 
 { 
 	var   childs=parentNode.childNodes; 
 	for(var   i=0;i <childs.length;i++) 
 	{ 
 		if(childs[i]==childNode) 
 		return   true; 
 		if(childs[i].hasChildNodes()) 
 		nodecheck(childs[i],childNode); 
 	} 
 	return   false; 
 } 
 var   testfun=function() 
 { 
 	var   e1=document.getElementById( 'ROOT '); 
 	var   e2=document.getElementById( 'A '); 
 	alert(nodecheck(e1,e2)); 
 } 
  </script>  
  </head>  
  <body   onload= "testfun(); ">  
  <div   id= "ROOT ">  
 	 <div   id= "A ">  
 		 <div   id= "AA ">  
 			 <div   id= "AAA ">  
 				Hello 
 			 </div>  
 		 </div>  
 	 </div>  
 	 <div   id= "B ">  
 		 <p   id= "BA ">  
 			 <input   id= "BAA "   type= "text "   />  
 		 </p>  
 		 <p   id= "BB ">  
 			 <input   id= "BBA "   type= "button "   value= "lala "   />  
 		 </p>  
 	 </div>  
 	 <div   id= "C ">  
 			 <select   id= "CA ">  
 				 <option   id= "CAA "> 1 </option>  
 				 <option   id= "CAB "> 2 </option>  
 				 <option   id= "CAC "> 3 </option>  
 			 </select>  
 	 </div>  
  </div>  
  </body>  
  </html>  
 ============================================================== 
 目的:输入一个节点A,再输入一个节点B,判断B节点是否是A节点的子节点 
 是返回true      否返回false   
 	var   e1=document.getElementById( 'ROOT '); 
 	var   e2=document.getElementById( 'A '); 
 返回true      A是ROOT的子节点   
 	var   e1=document.getElementById( 'ROOT '); 
 	var   e2=document.getElementById( 'AA ');   
 为什么返回false? 
 是这个比较判断   childs[i]==childNode      出现问题了么?
------解决方案--------------------用遍历吧 
 判断B是否是A的子节点   
 function isChild(A,B){ 
     for(var i=0;i <A.childNodes.length;i++){ 
         if(A.childNodes[i]==B){ 
             return true; 
         } 
     } 
     return false; 
 }
------解决方案--------------------var testfun = function() 
        { 
             var e1 = document.getElementById( 'ROOT '); 
             var e2 = document.getElementById( 'A '); 
             while (e2.parentNode) { 
                 if (e2 == e1) 
                     return true; 
                 e2 = e2.parentNode; 
             } 
             return false; 
         } 
 这样判断比较简单咯