I really don't like the idea of using proxies simply to essentially create an
array with a custom prototype.
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>
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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