How can i call a server side button click function from client side?

option is to simulate Click of a button using javascript.
<asp:Button ID="savebtn" runat="server" OnClick="savebtn_Click" style="display:none" />
HTML markup will look like this:

<button id="btnsave" onclick="fncsave()">Save</button>
now simulate a Click using JS

<script type="text/javascript">
     function fncsave()
     {
        document.getElementById('<%= savebtn.ClientID %>').click();
     }
</script>