How to run a javascript function before postback of asp.net button

Question

I have an asp.net button which is runat server, there is a function handle that postback of button onclick.

How can I display a "loading ..." word in the page before going to the server procedure?

Answer 1

Hook up OnClientClick to some javascript function that returns true or false. The postback occurs if it returns true else it is canceled.

  <asp:Button id="MyButton" runat="Server" Text="Close" 
                       OnClientClick="return  PromptClose();"/>


  <script type="text/javascript">
   function PromptClose(){
       return prompt("Do you really want to close this window?");
   }
  </script>