Allen Wirfs-Brock wrote:
On Feb 2, 2012, at 1:38 PM, Brendan Eich wrote:
keys etc. are currently spec'ed to to do own-only, you want allKeys to
do the crazy thing:
http://wiki.ecmascript.org/doku.php?id=harmony:iterators#standard_api
Let's not go around and around on this. Enumerable proto-properties
are harmful, no one wants them.
I'm afraid I have to disagree with the absolutism of this statement.
There are some perfectly reasonable use cases for enumerating proto
properties and they are quite in alignment with prototypal inheritance.
For example, how about defining a set of default property values and
then using prototypal inheritance to selective over-ride them:
let privateImplicitOptions = {a:1,b:2,c:3 /* and on and on */};
function makeOptions(explicitOptions) {
let opt = Object.create(privateImplicitOptions);
for (let [k.,v] of items(explicitOptions)) opt[k]=v;
return opt;
}
myOpts = makeOptions({b:-2});
Why should somebody I pass an options object to need to worry about
whether I used zero, one, or n levels of prototypes to represent by options.
+1
that said, I think we agree that the real problem is the legacy ES
semantics of for-in and its use (or lack of) for the enumerable
attribute. If we can start out with a clean slate conceptual slate for
for-of maybe we don't have to worry about such things. However, carrying
over a lot of historic baggage isn't a clean slate. Thinking in terms of
abstract collections, having keys() not mean "all keys in the
collection" seems quite absurd. That should be the normal case, the more
verbose name should be used for the exceptional case that excludes some
of the keys. Now in this case, the real problem is in deciding the
default way to view a plain Es objects as an abstract collection. Maybe
only considering own properties as the collection elements is the right
thing. In that case it may be "allKeys" that is carrying the wrong
implication and instead it should be something like "extendedKeys".
deepKeys, maybe?
Allen
Herby
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