解决IE下createElement的name不可写的问题

<script type="text/javascript">
<!--
    function createButton(){
        var oInput;
        if(document.all){ // IE
            oInput = document.createElement("<input type='hidden' name='aa'>");
        }else{ // FF
            oInput = document.createElement("input");
            oInput.type = "hidden";
            oInput.name = "aa";
        }
        document.body.insertBefore(oInput, document.body.firstChild);
    }

    function getInput(){
        alert(document.getElementsByName("aa").length)
    }
//-->
</script>
<input type="button" value="createButton" onclick="createButton()" />
<input type="button" value="getInput" onclick="getInput()" />