救急～～，帮解决一下，多谢了～～

<html>
<head>
<script language="javascript">var idx = 0;
function addnew(){
idx = idx + 1;
alert(idx)
var spanDemo = document.getElementById("DEMO");
spanDemo = spanDemo.cloneNode(true);
spanDemo.id = "DEMO"+idx;spanDemo.style.display='block';
spanDemo.innerHTML='<input type="radio" name="rad'+idx+'"><input type="radio" name="rad'+idx+'">'//var txtObj = spanDemo.getElementsByTagName("input")[0];
//txtObj.name = "rad"+idx;
//alert(txtObj.name)
//txtObj.id = txtObj.name;
//
//var txtObj1 = spanDemo.getElementsByTagName("input")[1];
//txtObj1.name = "rad"+idx;
//txtObj1.id = txtObj1.name;var spanObj = document.getElementById("Dynamic");
spanObj.appendChild(spanDemo);
}
</script>
</head>
<body>
<span id="DEMO" style="display:none">
<input type="radio" name="rad">
<input type="radio" name="rad">
</span>
<span id="Dynamic"></span>
<input type="button" name="btn" id="btn" value="add new" onclick="addnew()">
</body>
</html>