Symbol.hasInstance and [[Get]] vs [[GetOwnProperty]]

Jason Orendorff jason.orendorff at
Tue Aug 16 12:38:11 UTC 2016

On Mon, Aug 15, 2016 at 8:45 PM, /#!/JoePea <joe at> wrote:

> It seems like using [[Get]] for looking up `@@hasInstance` can be
> confusing and requires devs to write extra code.

I think the emotionally loaded words in this post ("fail", "ugly",
"fragile", "break") are unhelpful. You have to make your point some other

The `c instanceof B` check (arguably unintuitively) fails.

It doesn't "fail". B inherits behavior from its base class A. That's the
whole point of subclassing.

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