On Wed, Oct 1, 2014 at 4:17 PM, Axel Rauschmayer <a...@rauschma.de> wrote:
> On Oct 1, 2014, at 22:12 , Axel Rauschmayer <a...@rauschma.de> wrote: > > 1. Transforming iteration methods > > We're currently polyfillying the `Map`, and got some questions form devs. > One of them is about transforming iteration methods, like `map` and > `filter`. > > Unfortunately I missed that part of the spec when it was approved, so can > someone please remind/clarify -- was it an intended decision not to hap > Map#map, Map#filter? I can see only Map#forEach in the spec. Are maps > "immutable"? -- That's fine, the `map` and `filter` return a new map. > > > FWIW: I’ll probably use the following work-arounds. I don’t expect > performance to be an issue for my applications; it’d be interesting to hear > if it becomes a problem for someone. > > ```js > let map2 = new Map(map1.entries().filter((key, value) => key >= 0)); > let map2 = new Map(map1.entries().map((key, value) => [key * 2, value * > 2])); > > entries() returns an iterator, not an array. Rick
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