Hide ModalPopup Using Javascript

When I first started using Asp.Net Ajax toolkit, I found there is a very fundamental requirement from lot of developers where we want to have some kinds of control on the client side without triggering the service side event.

Asp.net Code is Like below::

<asp:Panel runat="server" ID="pnlDemo" style="display:none">

          <h1>This panel is a test demo</h1>       

        </asp:Panel>
        

     <cc1:ModalPopupExtender ID="ModalPopupExtender" runat="server"  TargetControlID="linkButton1"

                 PopupControlID="pnlDemo"

                BackgroundCssClass="modalBlockBackground" BehaviorID="ModalPopupExtender"

               DynamicServicePath="" Enabled="True">

         </cc1:ModalPopupExtender>

   if(!show)
       {
       $find('ModalPopupExtender').hide();
       }
       else
       {
           $find("ModalPopupExtender").show(); 
       }