+1 also to not use iteraros by default when the use case never needed one
On Sat, Dec 7, 2013 at 10:45 AM, Tom Van Cutsem <[email protected]> wrote: > As currently specified, [[OwnPropertyKeys]] doesn't have any particular > invariants on the values it generates from the returned iterator. > > Mark and I proposed to reintroduce [[GetOwnPropertyNames]] as a separate > internal method, which would return an array rather than an iterator, but > which would also be required to return at least the names (symbols or > strings) of all non-configurable properties. The switch to an array return > value is motivated partly by the reasons Jason stated, but also because > actually checking the invariant requires exhausting the iterator anyway. > > [[OwnPropertyKeys]] would continue to return an iterator (or iterable , as > Jason suggests, which seems to make more sense), but there would be no > invariants on its generated values. > > [[GetOwnPropertyNames]] would be the reliable way of querying an object > for its own properties, and would be used at least by > Object.getOwnPropertyNames and the abstract operations used by > Object.{freeze,isFrozen,seal,isSealed}, so that the result of these > operations can in turn be made reliable. > > [[OwnPropertyKeys]] can be used for all other operations that don't need > the invariant that all non-configurable properties should be > listed/generated. > > Cheers, > Tom > > > 2013/12/6 Allen Wirfs-Brock <[email protected]> > >> 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 >> > > > _______________________________________________ > es-discuss mailing list > [email protected] > https://mail.mozilla.org/listinfo/es-discuss > >
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