Setting window.onbeforeunload to undefined in IE8 causes" not implemented error

Question

            if(!$('fieldset.quote-step4').hasClass('show')) {
                window.onbeforeunload = function() {
                    return "Are you sure you want to leave the quote request page? This will reset the form.";
                }
            } else {
                window.onbeforeunload = undefined;
            }

I have the above in a script inside of a private function that's causing a "not implemented" error in ie8.

The specific line that causes the error is: window.onbeforeunload = undefined;

From what I've read in other questions window should be declared as a local variable to fix this issue-- but I'm not sure how.

Can anyone explain this bug to me and a possible solution?

Thank you!

Answer 1

Try this:

$(window).on('beforeunload', function() {
   if($('fieldset.quote-step4').hasClass('show')) {
        return;
   }
   return "Are you sure you want to leave the quote request page? This will reset the form.";
});

And it is not the best idea to use DOM1 Handlers when jQuery is already on your page.

Answer 2

window.onbeforeunload = function(){};

Answer 3

onbeforeunload is an event handler; apparently; IE8 doesn't like clearing it.

You can simply set it to a function that doesn't return anything.