getOwnPropertyDescriptor side effects

Isiah Meadows isiahmeadows at
Wed Jan 11 11:47:48 UTC 2017

Really, the only thing that matters is in fact *observable* behavior, so
I'd concur. I just get the feeling several people in this thread don't
quite understand that part of the spec, or in a few cases, the spec itself
and its invariants.

On Wed, Jan 11, 2017, 04:17 Raul-Sebastian Mihăilă <raul.mihaila at>

> The actual semantics of objects, in ECMAScript, are specified via
> algorithms called internal methods. Each object in an ECMAScript engine is
> associated with a set of internal methods that defines its runtime
> behaviour. These internal methods are not part of the ECMAScript language.
> They are defined by this specification purely for expository purposes.
> However, each object within an implementation of ECMAScript must behave as
> specified by the internal methods associated with it. The exact manner in
> which this is accomplished is determined by the implementation.
> So, the sentence 'having an internal slot for the value of .stack would be
> a spec violation' doesn't make sense to me because the slots are a
> specification concept. I guess an implementation can represent this concept
> one way or another internally, but it doesn't matter as long as the
> implementation behaves as specified.
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