On 25/09/2010, at 08:39, Brendan Eich wrote:
> On Sep 25, 2010, at 1:51 AM, Jorge wrote:
>> On 25/09/2010, at 01:28, P T Withington wrote:
>>> On 2010-09-24, at 18:11, Jorge wrote:
>>>
>>>> So b is truly a subclass of Array, not a fake one.
>>>
>>> I stand corrected. At some time in the past, this did not work for me.
>>> Apparently things have improved!
>>
>> But you are right too: neither .__proto__ nor Array.create() are in the
>> specs, so there's no way to subclass an Array in ES5.
>
> ES5 supports initializing __proto__ on a new object, just not setting the
> prototype of an object after it has been created:
>
> var arrayLike = Object.create([]);
But that's exactly what P T Withington was calling a fake array. To make it a
true Array you'd need ES5 to have an Array.create() or .__proto__, because :
a= Object.create([]) ; a[2]=27 ; [a.length, a]
-> [ 0, [undefined, undefined, 27] ]
And:
a.length= 1 ; [a.length, a]
-> [ 1, [undefined, undefined, 27] ]
A true Array.create() would be:
function Array.create (proto) {
if ( !(proto instanceof Array)) {
throw Error("Proto must necessarily be an instance of Array");
}
var newArray= []; // <- get the special [[ put ]]
newArray.__proto__= proto;
return newArray;
}
That, or an inheritable special [[ put ]], as you have said before:
https://mail.mozilla.org/pipermail/es-discuss/2009-December/010424.html
--
Jorge.
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