On Oct 1, 2010, at 6:24 PM, Oliver Hunt wrote:
> I really don't like the idea of using proxies simply to essentially create an
> array with a custom prototype.
Implement proxies, then we'll talk :-P.
> My understanding of what is wanted (in terms of subtyping an array) is an
> ability to have something like
>
> var arr = new MyArray()
>
> Where 'new MyArray' behaves in essentially the same manner as 'new Array',
> however it produces an object along the lines of
>
> <an array instance> <- <a custom prototype> <- <array prototype>
I don't think the use-case is satisfied by a direct Array instance, whatever
its proto. That's the rub.
/be
>
> In a engine that support mutating proxies this would be equivalent to:
>
> function MyArray() {
> var result = Array.apply(null, arguments);
> result.__proto__ = MyArray.prototype;
> return result;
> }
>
> MyArray.prototype = Object.create(Array.prototype);
>
> If my understanding of this desired behaviour is correct, i think a better
> solution would be to make an API that could generate the MyArray function.
>
> --Oliver
>
>
> On Oct 1, 2010, at 6:14 PM, Brendan Eich wrote:
>
>> KangaX brought this up in
>>
>> http://perfectionkills.com/how-ecmascript-5-still-does-not-allow-to-subclass-an-array/
>>
>> and proxies are of no avail. To make an array-like using ES5 is possible but
>> [[Class]] won't lie, and that is still true with Proxy.create instead of
>> Object.create.
>>
>> As we have discussed, [[Class]] is very much a nominal type tag, so it is
>> not something we want to be forged by an impostor. But perhaps as Allen
>> mentioned in the TC39 meeting this week, [[ClassName]] could be separated
>> from [[Class]], and forged without problem. Proxies would want to be able to
>> present a specific [[ClassName]], but a non-varying one -- so probably a
>> trailing Proxy.create parameter. Thoughts?
>>
>> /be
>>
>>
>>
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>
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