Set.prototype.entries: indices as keys?
brendan at mozilla.org
Mon Jan 19 11:27:41 PST 2015
Brendan Eich wrote:
> Dmitry Soshnikov wrote:
>> let [x,y] = set; // x='a'; y='b’;
>> Would this work actually? :) Destructuring does get property, which
>> wouldn't call set's `get` method.
> -- destructuring array patterns uses the iteration protocol, which is
> why the line works as Axel suggested:
> js> let set = new Set(['a', 'b']);
> js> let [x,y] = set;
> js> console.log(x, y)
> a b
> js> for (let elt of set) console.log(elt)
> But not all iterables are indexable, nor should they be.
As you've pointed out (several times ;-), the odd duck is forEach.
Set.prototype.forEach passes element as key and value. But sets cannot
be indexed by values (to get booleans, as one might expect -- and even
Sets should not be indexable but should be iterable. This leaves forEach
with the dilemma of having a different signature on Set than Map and
Array, or else taking a dummy or redundant parameter as the forEach key.
Or we could leave forEach out of Set.prototype -- that's quite a better
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