Finiteness of object properties set

David Bruant david.bruant at
Wed Sep 7 05:07:07 PDT 2011

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
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.

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).


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