[Harmony Proxies] Proposal: Property fixing

Brendan Eich brendan at mozilla.com
Thu Jun 16 21:01:12 PDT 2011

On Jun 16, 2011, at 8:58 PM, Cameron McCormack wrote:

> Mark S. Miller:
>> Although
>> <http://wiki.ecmascript.org/doku.php?id=strawman:proto_operator>
>> still appears in "strawman", I believe we accepted its functionality
>> (with concrete syntax still TBD) into ES-next "proposal" status, so
>> it will become standard at the same time proxies will. Of course, the
>> current WebIDL JS binding is targeting ES5 and so cannot directly rely
>> on either proxies or "<|". But perhaps we should choose an ES5 host
>> behavior for array host objects that anticipates reimplementing them
>> using "<|" rather than proxies in the ES-next timeframe? Perhaps we
>> should choose an ES5 behavior that leaves both future choices open? It
>> sounds like we're already either there or almost there.
> Maybe I was too eager: I guess subclassing array objects in this way
> wouldn’t let us define arrays that are read only, or fixed length, or
> whose values could be changed by the implementation at any time.  Is
> that right?  If so, maybe array subclassing isn’t what we want here, and
> using proxies with the Array prototype object in the prototype chain is
> the way to go.

Read-only and fixed length array subclassing should not require using a proxy to implement the subclass.

The value changing at any time should be ok as long as length is writable. Non-writable length value should not change (assuming non-configurable -- if configurable then reconfiguring to writable would allow new values to be put).


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