On Oct 6, 2011, at 12:30 PM, Brendan Eich wrote:
> My point was that your "PrototypeJS and Firebug pre-date .hasOwnProperty()"
> chronology was wrong. Object.prototype.hasOwnProperty was around since ES3.
> It was not used in Prototype, but on the other hand, the "never extend
> Object.prototype" rule was also promulgated.
JJB has it mostly right. When Sam wrote Object.extend (which was originally
Object.prototype.extend), it didn't use hasOwnProperty; my guess is that Sam
didn't know about it, because most of us were JavaScript amateurs back in the
day, including myself. When I joined the project over a year later, I remember
discussing this problem and discovering that Safari 2.0 didn't support
hasOwnProperty. That, plus the hazard of changing implementation behavior, led
us to leave things as they were. If I were writing Prototype's Object.extend
from scratch, I'd definitely want it to copy "own" properties only.
Anyway, I'm in favor of standardizing Object.extend in ES6, but in a way that
considers only "own" properties (including private names, if so desired). I
don't think ES6 should copy the exact behavior of Prototype's (flawed) version
of Object.extend. Whether that takes the form of a method named "Object.extend"
or a .{ operator… well, that's less important to me, but my vote is for the
former.
(Keep in mind that the 80% use-case for this sort of thing is merging default
options with user-supplied options, at least in the code I write. That's a
simple case that usually involves merging two plain objects without interesting
__proto__ values. That's not to say that we should ignore the edge cases; but
let's just keep them in the proper perspective, and not let them hold up
progress on this front.)
Cheers,
Andrew_______________________________________________
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