How to Get Html input file URL from javascript

<asp:fileupload id="FileUpload1" runat="server" onchange="test(this);" xmlns:asp="#unknown" />
<asp:hiddenfield id="HiddenField1" runat="server" xmlns:asp="#unknown" />

<script language="javascript" type="text/javascript">

       function test(Obj) {
           document.getElementById('<%=HiddenField1.ClientID %>').value = Obj.value;
           
       }
   </script>