Perhaps @@unscopable shouldn't be a Set...

Axel Rauschmayer axel at
Wed Apr 30 10:14:14 PDT 2014

> Specifying the duplicated lookup is doable but a pain.  That and the semantic issues WRT proxies makes me a lot less comfortable with the added complexity of supporting @@unscopable.

I never liked it. It burdens the language in order to support legacy code. Are there other ways of fixing the problem?

A few, probably silly, ideas, for the sake of brainstorming:

* Hard-coding `with` to ignore only Array.prototype.values.
* Patching the problematic libraries somehow.
* Use a property attribute to signal to `with` that a property should be ignored. [[Enumerable]] would be perfect, but unfortunately won’t work.

Somehow, we have to put the burden on `with` and the legacy code instead of the future-facing parts of the language.


Dr. Axel Rauschmayer
axel at


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