how to PREVIEW IMAGE without any click

Default.aspx

<script type="text/javascript">
        function preview(img)
        {
            var a = document.getElementById("<%=Image1.ClientID %>");
            a.src = img.value;
        }
</script>



 <asp:FileUpload ID="FileUpload1" runat="server" onchange="preview(this)" />

<asp:Image ID="Image1" runat="server" Width="80" Height="80" />