From: Brendan Eich [mailto:[email protected]]
> 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. This seems like it'd involve too much machinery and give unexpected results. I'd expect `instance.map(...)` to return another one of `instance`. That is, given a MapIterator `i`, I'd expect `i.map(...)` to be another MapIterator, and not a Map like you are proposing. Giving a MapIterator also has the advantage of preserving laziness. I like how in > ```js > var newMap = new Map(oldMap.entries().map((([k, v]) => [k + 1, v+ 1]); > ``` The Map constructor call gives a clear delineation of where the iterator is being consumed, and the laziness is flattened down. Whereas if `.entries().map(...)` gave a Map instance straightaway, the option of keeping things lazy would be gone. _______________________________________________ es-discuss mailing list [email protected] https://mail.mozilla.org/listinfo/es-discuss
