Displaying a confirmation box inside javascript unload event

HI,
I have added an unload event to my page like :
window.addEventListener('unload', function(event) {
    if(cancel === false) {
        return "Changes you made will not be saved";
    }
});

Bascially when unloading happens i want a confirmation dialog to appear
with two buttons ok and cancel. And if user presses ok then proceed with the normal flow otherwise stop closing of the current window.

But somwhow the dialog itself is not appearing. Many places say that
you cannot have confirmation dialog from inside an unload event so i tried returning a string but that also didnt work.
I am making it work in chrome .

Thanks
Rohit BajajAsked:
Who is Participating?
I wear a lot of hats...

"The solutions and answers provided on Experts Exchange have been extremely helpful to me over the last few years. I wear a lot of hats - Developer, Database Administrator, Help Desk, etc., so I know a lot of things but not a lot about one thing. Experts Exchange gives me answers from people who do know a lot about one thing, in a easy to use platform." -Todd S.

Julian HansenCommented:
Try

window.onbeforeunload = function(){
  return 'Changes you made will not be saved';
};

Open in new window

Experts Exchange Solution brought to you by

Your issues matter to us.

Facing a tech roadblock? Get the help and guidance you need from experienced professionals who care. Ask your question anytime, anywhere, with no hassle.

Start your 7-day free trial
Rohit BajajAuthor Commented:
This does not work. Setting breakpoints the code is not reachable!! This is happening most likely because my web application is opened inside an iframe and close button is not part of my application. So although window.addEventListener('unload' this was getting executed but problem was with confirmation dialog. The code mentioned by you is ignored.
It's more than this solution.Get answers and train to solve all your tech problems - anytime, anywhere.Try it for free Edge Out The Competitionfor your dream job with proven skills and certifications.Get started today Stand Outas the employee with proven skills.Start learning today for free Move Your Career Forwardwith certification training in the latest technologies.Start your trial today
JavaScript

From novice to tech pro — start learning today.