getBackgroundPage instanceof

[Maksim Ivanov]

Hello,

The object that's returned by chrome.runtime.getBackgroundPage() gives false when called with "instanceof Window". I presume it's because the background page's Window interface is not the same as other pages' Window interfaces.

Does anyone know what's the actual type of that object, so that "instanceof <something>" can evaluate to true? Or at least how to detect inside some random function that it received another page's Window object?

Thanks,

Maksim

[hrg...@gmail.com]

Window objects that belong to different browsing contexts have different constructors, so you cannot use instanceof to test their type.

Instead you can do this:

bgPage.constructor.name == "Window"

[Maksim Ivanov]

Thanks for the quick response!

Is there a way to make it a bit more reliable, because I guess the ".constructor.name" approach is suspect to false positives like this:

{'constructor': {'name': 'Window'}}

or just:

{'constructor': Window}

[hrg...@gmail.com]

You can try something like this is you are really paranoid: 

 

bgPage.__proto__.constructor.name == "Window"

Or

bgPage.__proto__[Symbol.toStringTag] == "Window"

But keep in mind that __proto__ is deprecated.

[hrg...@gmail.com]

I've just realized you can also do this:

bgPage instanceof  bgPage.Window

which is what you were originally asking.

[Empathic Awakened Cancerian]

Who said anything about being paranoid the browser is working like it is

Get Outlook for Android

---

From: chromium-...@chromium.org <chromium-...@chromium.org> on behalf of hrg...@gmail.com <hrg...@gmail.com>
Sent: Tuesday, December 14, 2021 4:00:10 AM
To: Chromium Extensions <chromium-...@chromium.org>
Cc: hrg...@gmail.com <hrg...@gmail.com>; em...@chromium.org <em...@chromium.org>; Chromium Extensions <chromium-...@chromium.org>
Subject: [crx] Re: getBackgroundPage instanceof

 

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