为什么if (node.attributes != null)正确，而if(node.attributes.length!=0)却出现错误

[bbrr]

请问
为什么下面的函数会出错，
function Traverse(node)
{
nodes+=1;
if(node.attributes.length!=0)
nodes+=node.attributes.length;
for(var i=0;i<node.childNodes.length;i++)
Traverse(node.childNodes(i));
}
而下面这个却成功
function Traverse(node)
{
nodes+=1;
if(node.attributes!=null)
nodes+=node.attributes.length;
for (var i=0;i<node.childNodes.length; i++)
Traverse(node.childNodes(i));
}

[saucer]

because some node has no attributes? then when you call node.attributes.length, it will complain node.attributes is null, you cannot access a null object's length property, since there is none

note, text is also a node, but it doesn't have an attributes property, for example:
<xml id="xmldoc">
<root>hello</root>
</xml>
<script language="javascript">
function window.onload()
{
var doc = xmldoc.documentElement;
alert(doc.attributes.length);
alert(doc.childNodes.length);
alert(doc.childNodes[0].nodeName + " has attributes? " + doc.childNodes[0].attributes)
}
</script>

[bbrr]

谢谢大侠指点。
我想说一声，这里的论坛真不错。