need a pop on close window

[Kriti09]

I need a message appear on pop up when user try to close window. I tried close.window() but that is not working for mozilla.

[JShor]

Events when a window is being closed is handled by the onbeforeunload event.

function confirmClose() {
    if (confirm("This is an confirm box.")) {
      parent.close();
    }
    else
      // User does not want to close the window.
 {
    }
}

window.onbeforeunload = confirmClose();