ArrayClass should imply @@isConcatSpreadable

Jonas Sicking jonas at
Mon Oct 28 16:54:24 PDT 2013

On Mon, Oct 28, 2013 at 4:13 PM, Anne van Kesteren <annevk at> wrote:
> On Mon, Oct 28, 2013 at 8:20 PM, Boris Zbarsky <bzbarsky at> wrote:
>> In terms of existing ArrayClass objects that are shipping on the web right
>> now, Gecko is shipping (though perhaps not in final releases yet) the .ports
>> of a MessageEvent and the return value of getClientRects(). I _think_
>> changing the concat() behavior of these should be OK. Certainly for .ports,
>> which we haven't been shipping for very long at all.
>> Thoughts?
> Could we still change those to actual arrays? I guess for .ports that
> might be trickier as it implies a readonly view.

Lets just return a frozen Array. I know that people on TC39 has said
that it's ugly, but I still think it's far less ugly than creating a
whole pile of host classes just because we lack immutable arrays.

> ArrayClass feels like a hack.


/ Jonas

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