I'm working with TomVC right now on revising these internal methods. More on that soon.
One possible advantage of using an Iterator is that large dense indexable objects such as typed arrays, strings, or similar abstractions defined using a proxy don't have to instantiate an Array containing huge numbers of element indices. Also we have talk about, the future addition of user land iterator valued functions such as keys, ownKeys, etc. or the possibility of frameworks providing such functions. The internal methods. The MOP defined by the internal methods should provide a stable foundation for such future extensions. Allen On Dec 6, 2013, at 6:35 AM, Jason Orendorff wrote: > It looks like [[OwnPropertyKeys]] is defined to return an iterator. > But the ordinary [[OwnPropertyKeys]] method produces the List of keys > to be iterated eagerly, and pretty every place that calls the method > immediately consumes the entire iterator. So there is no actual > laziness. > > This is weird. I think it would be clearer for [[OwnPropertyKeys]] to > return a List of PropertyKeys. > > Except for proxies, this doesn't change behavior. Here are the changes > needed to implement this: > > * In 9.1.12, the ordinary object [[OwnPropertyKeys]] method, change > step 3 to just say "Return keys." instead of "Return > CreateListIterator(keys)." > > * In 9.5.12, the Proxy [[OwnPropertyKeys]] method, treat the return > value as an iterable (not an iterator) and convert it to a List of > PropertyKeys using IteratorStep, IteratorValue, and ToPropertyKey. > Change the NOTE to describe the new invariant. > > * In 19.1.2.1 Object.assign, 19.1.2.8.1 GetOwnPropertyKeys, 19.1.2.14 > Object.keys, and 19.1.2.15.1 MixinProperties, drop the IteratorStep > boilerplate. > > * In 26.1.10 Reflect.ownKeys(), convert the result of calling > [[OwnPropertyKeys]] to an Array using CreateArrayFromList. > > Note that 7.3.10 SetIntegrityLevel and 7.3.11 TestIntegrityLevel > already assume that [[OwnPropertyKeys]] returns a List, as proposed. > > -j > _______________________________________________ > es-discuss mailing list > [email protected] > https://mail.mozilla.org/listinfo/es-discuss > _______________________________________________ es-discuss mailing list [email protected] https://mail.mozilla.org/listinfo/es-discuss
