Javascript code for change Decimal to a Hexadecimal Value ?

<script  type="text/javascript">
    function hexa()
    {
   var txtHexa=document.getElementById('txtHexa').value;
   alert(txtHexa.toString(16));
    }
   </script>

<div>
       <asp:TextBox ID="txtHexa" runat="server"></asp:TextBox><input id="Submit1" type="submit" onclick="hexa()"
           value="submit" />
   </div>