在js里添加radio标签怎样给标签设置name属性？？？

var b = document.createElement("<INPUT name='a'>");

<body>
</body>
<script>
var b = document.createElement("<INPUT type=radio name='a'>");
var t =  document.createTextNode("aa");
document.body.appendChild(b)
document.body.appendChild(t)b = document.createElement("<INPUT type=radio name='a'>");
t =  document.createTextNode("bb");
document.body.appendChild(b)
document.body.appendChild(t)
</script>
The NAME attribute cannot be set at run time on elements dynamically created with the createElement method. To create an element with a name attribute, include the attribute and value when using the createElement method
谢谢楼上两位，但都不兼容firefox...
不知道firefox有什么方法。。
if(!document.all){//FF
   var a = document.createElement("INPUT");
   a.type="radio";a.name = "ba";
   document.body.appendChild(a);
}
else{//IE
   var b = document.createElement("<INPUT type=radio name='a'>");
   var t =  document.createTextNode("aa");
   document.body.appendChild(b)
   document.body.appendChild(t)
}