All modern browsers support the JavaScript's window.onbeforeunload
event. It fires before the unload
event when the page is unloaded. So this event always uses to stop a page from exit. The following codes illustrate how to implement this function:
window.onbeforeunload = function (e) {
var message = 'Are you sure you want to leave?';
var e = e || window.event;
// For IE and Firefox prior to version 4
if (e) {
e.returnValue = message ;
}
// For Safari
return message;
};
and we can also use this event to disable button before postback is done or form is submitted so that user cannot click button again. It is very simple.
window.onbeforeunload = function () {
document.getElementById("<%=Button1.ClientID %>").disabled = true;
};