Beforeunload for PWA

Jordan Harband ljharb at
Tue Mar 30 16:27:44 UTC 2021

PWAs and events aren't part of the JS language; see

On Tue, Mar 30, 2021 at 5:39 AM Adam Eisenreich <akxe at> wrote:

> I think that PWA should have the ability to override the default
> beforeunloadEvent message.
> Since returning string is already deprecated and removed from all
> browsers, it would be safe to change how the returned value is handeled.
> *All proposed changes should only apply to installed PWAs!*
> If the return value is:
>    1. HTMLFormElement - display the element in front of everything with a
>    backdrop disabling every other interaction.
>    * CSS of the page should apply to this element.
>    * Browser listens to the "submit" event of the form; based on the
>    truthiness of the return value from the form submit event either close
>    window or hide message while keeping window open
>    * Closing the window via system buttons a second time (while dialog is
>    open) will force the closing of the page.
>    2. String - Display the standard beforeunload dialog that used to have
>    the custom message.
> What are your thoughts? Should PWA have the exception and have elevated
> possibilities?
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