New Harmony built-in native objects APIs

Brendan Eich brendan at mozilla.com
Thu Aug 12 14:44:16 PDT 2010


On Aug 12, 2010, at 2:07 PM, Erik Arvidsson wrote:

> It seems like ES5 does not define the [[Enumerable]], [[Configurable]]
> nor [[Writable]] for the fields on Array.prototype and others like it.

It does, by specifying default values in the intro to Clause 15, last paragraph:

In every case, the length property of a built-in Function object described in this clause has the attributes { [[Writable]]: false, [[Enumerable]]: false, [[Configurable]]: false }. Every other property described in this clause has the attributes { [[Writable]]: true, [[Enumerable]]: false, [[Configurable]]: true } unless otherwise specified.

ES1-3 did likewise, IIRC.


> I spec'ed the attributes for all the methods to match ES+Reality. This
> means that the methods have {enumerable: false, configurable: true,
> writable: true}. This matches what JSC, V8, SpiderMonkey and IE9p4 do.

ES5 has your back ;-).


> In the future, it would be good if we could follow the existing
> semantics for the built-in natives.

Agreed.

/be


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