Dmitry Soshnikov wrote:
From: es-discuss [mailto:[email protected]] On Behalf Of Domenic
Denicola
- show quoted text -
> Unless I'm missing something (quite possible!), I would prefer not to add
new methods to Map and Set when they could be added to %IteratorPrototype%.
Yeah, I'm missing something. It's the difference in code between:
```js
var newMap = oldMap.map(([k, v]) => [k+ 1, v+ 1]);
```
versus
```js
var newMap = new Map(oldMap.entries().map((([k, v]) => [k+ 1, v+ 1]);
But entries returns an iterator, and if we define %IteratorPrototype% to
create a new instance of the right class given its |this| parameter, in
this case Map and not MapIterator, then no need for the new Map() wrapper.
I think I still prefer avoiding every iterable subclass adding its own
map/filter/etc. in favor of people using the compositional base primitives, but
at least I see the argument now.
I point out in https://www.w3.org/Bugs/Public/show_bug.cgi?id=26973#c3
that the lack of Map.prototype.{map,filter,...} doesn't bite when you
use for-of, but of course will be missed when you want to call
someMap.filter directly. Which is reasonable to do!
/be
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