On Sun, Dec 19, 2010 at 7:21 AM, Lasse Reichstein <
reichsteinatw...@gmail.com> wrote:
> On Sun, 19 Dec 2010 08:39:00 +0100, Juriy Zaytsev <kan...@gmail.com>
> wrote:
>
> __proto__ also appears to be marked as "deprecated" in current version of
>> corresponding MDN docs. I wouldn't be surprised to see it go soon (if that
>> doesn't break web too much).
>>
>
> I'm afraid I don't see it going away any time soon.
> For one thing, it probably will break some parts of the web (although I'm
> happy
> to see that, e.g., JQuery and ext.js don't use it).
>
Most definitely will break the web. Question is — how badly. __proto__ is
non-standard, and it's been repeated hundreds of time — as part of web
scripting best practices — not to rely on non-standard features (and prefer
standard ones over them). But of course that's not how the web rolls :)
>
> Also, it provides a feature that ES5 doesn't yet: the ability to change an
> object's
> prototype chain. ES5 brought us Object.getPrototypeOf, but no
> setPrototypeOf.
>
This was a conscious decision, as far as I know. Mutable [[Prototype]]
carries performance overhead. I think that was one of the concerns of some
of the TC-39 members. Mutable [[Prototype]] via "__proto__" also breaks
other things. IIRC, there was a bug in V8 where JSON.stringify({ __proto__:
[] }) serialized to "[]". This wouldn't happen with `Object.setPrototypeOf`
but performance would still be an issue, I suppose.
>
> And it's widely supported: Firefox, Opera, Safari and Chrome, and people
> are used
> to writing around IE anyway.
> It's extremely difficult to remove any feature that is already out there
> and supported
> by more than one browser.
>
Indeed.
Well, Mozilla has already deprecated magic __count__, then removed it from
FF4. I can imagine them removing __proto__ (or issuing a warning on
access/assignment) under strict mode. Other implementations could be more
problematic.
Is Brendan on this list?
[...]
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kangax
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