Safari: ArrayBuffers are sometimes not `instanceof ArrayBuffer`

Summary

I’m storing and retrieving ArrayBuffer objects from IndexedDB, and I noticed that in my test environment, the ArrayBuffer objects are not always instanceof ArrayBuffer in Safari. As a result, the Buffer package throws the following exception:

TypeError: First argument must be a string, Buffer, ArrayBuffer, Array,or array-like object.

This behavior does not occur in any other web browser.

Detailed Explanation

The test environment is that of the Karma test runner, which uses an iframe to isolate test code from the runner’s code. As a result, the ArrayBuffer constructor object in the code’s context is not referentially equivalent to the ArrayBuffer constructor object in the main window context. This is similar to the age-old Array problem, where arrays from other contexts are not necessarily instanceof Array, necessitating the use of Array.isArray.

Safari chooses the main window’s constructor for the ArrayBuffer object retrieved from IndexedDB, so it is not an instanceof ArrayBuffer in the test code’s context.

Here’s a screenshot, just so you know I’m not totally mad here. This is evaluated at a breakpoint in the stack frame that throws the TypeError:

I do not have a good solution to the problem without resorting to some hack (e.g., is the byteLength property present?).

[maximerety]

Hi!

I found this bug report while investigating a similar issue (not using the buffer library) and wanted to add two things:

• Thank you very much for saving me a lot of time!
• I’ve filed an issue on Webkit Bugzilla: https://bugs.webkit.org/show_bug.cgi?id=185906, so that it might be fixed some day.

Best regards,

[jvilk]

@maximerety Thanks for reminding me of this issue! I just added a minimal complete test case to that bug report.