2011/9/7 David Bruant <[email protected]> > Le 06/09/2011 17:59, Mark S. Miller a écrit : > > I agree that the spec should clearly state that a non-extensible object >> has a finite collection of own properties. Regarding infinite extensible >> objects, the only problem I see off the top of my head is: What would >> Object.getOwnPropertyNames return? >> > And what about for-in loops? :-p >
It's always possible to break/return early, no? Didn't iterators/generators already cross this bridge? An iterator could iterate over an infinite stream of values. > If this is really considered, the problem to solve is to express an > infinite set with a finite representation. RegExps may be a solution. One > big question is on RegExp expressivity: Can any infinite string set be > expressed with (a finite number of) JS RegExps? I have to admit that i know > ECMAScript pretty well expect RegExp i have never taken the time to > investigate, so i have no idea of the answer to this question, not even an > intuition. > I have no idea where you are taking this, but trying to map infinite sets of properties onto regular expressions seems like a horrible thing to do :-) > Alternatively, extensible objects could be stated as having a finite set of > properties. I have no knowledge of host objects with an infinite property > set and everyone's intuition falls under the idea that objects are a finite > collection of properties. > Saying it explicitely would prevent attempts from ES implementors to have > host objects with infinite property set. It would also allow to continue > proxies with the current design tracks (which currently prevent infinite > property sets). I see no problem with current proxies emulating an extensible object with an infinite set of properties. Object.getOwnPropertyNames could return [], claiming that all of these properties were inherited. Even with invariant enforcement, the FixedHandler does not enforce that getOwnPropertyNames returns all non-configurable own properties observed thus far. If these virtual properties are all marked non-enumerable, the "enumerate" and "keys" trap can return [] without lying. Regarding invariant enforcement: if the generated properties are marked non-configurable, the FixedHandler would require an unbounded amount of storage, so that's something to consider. But so as long as we're sticking to emulating an infinite series of non-configurable properties on extensible objects, I see no show-stopping issues. Cheers, Tom
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