Subj : Re: for/in loops
To   : Alex Fritze
From : Brendan Eich
Date : Tue May 11 2004 05:43 pm

Alex Fritze wrote:
> Hi,
> 
> A couple of questions about for/in:
> 
> 1.
> Getters & setters defined with __defineGetter__/__defineSetter__ are 
> currently not enumerated in for/in loops. Is there a reason for that?


Looks like a bug to me, especially in light of the prior getter= / 
setter= operators implemented by yours truly, on which __dG__ and __dS__ 
were based.  getter= and setter= were deprecated due to JS2 / ECMA-262 
Edition 4 forward compatibility concerns.

I'll fix in the 1.8a trunk.


> 2.
> The code
>   function f() { var x,y,z; }
>   f.foo = "bar";
>   for(var p in f) dump(p);
> yields
>   xyzfoo
> 
> Why are f's private variables enumerated?


Compatibility with the pre-ECMA Netscape JS implementations.  We could 
ditch this, but I'm not sure I wouldn't break something I care about. 
Does this break you?

ECMA allows extensions, although extending function objects with 
properties such as these makes for trouble.  See 
http://lxr.mozilla.org/mozilla/source/js/src/jsinterp.c#443 and surrounding.

/be

.