On Fri, Mar 11, 2011 at 10:07 AM, Claus Reinke <claus.rei...@talk21.com>wrote:
> I believe it is very very important that the ECMAScript standard specify >> that when a new Object is created, for..in iteration traverses properties in >> the order they are added, regardless of whether the properties are numeric >> or not. >> > > Some users might prefer 'in the order of keys'. That is predictable, > and allows for efficient implementation (both sparse and dense). > Are you suggesting changing the enumeration order which is currently implemented as "iteration order matches insertion order" under the careful set of conditions Allen enumerated earlier in this thread? (e.g. no enumerable props on prototype). If so - the thought of this makes me pretty nervous. There is undoubtedly significant amounts of code in the wild on the web which depend on the current enumeration order, and changing this would increase the size of the harmony-uptake tax (code audits and refactors). Someone -- Mark Miller? -- suggested an interesting option when this discussion came up last on this list (around Christmas 2010 IIRC). Basically -- enumerate named props in insertion order, and numeric props in numeric. This gets pretty close to what most developers seem to expect, while leaving the door wide open for fast implementation of array-like objects. > > Most of these are just awkward ways of saying "this > is the order I want" and "I also want hashmap access". So why not write > that out explicitly, with an optional ordering parameter, making the > enumeration explicit > when the default ordering isn't suitable: > You know, most of the time when I see valid use-cases for an alternate enumeration order, I can't help but think to myself: this might have a better solution if ES had generators, something like what Mozilla prototyped in JavaScript 1.7, and you could make such a generator the enumeration hook for the object in question. Wes -- Wesley W. Garland Director, Product Development PageMail, Inc. +1 613 542 2787 x 102
_______________________________________________ es-discuss mailing list es-discuss@mozilla.org https://mail.mozilla.org/listinfo/es-discuss
