On Mon, Oct 6, 2014 at 10:59 PM, Dmitry Soshnikov < [email protected]> wrote:
> Hi, > > We're currently polyfilling `Array.from` in our codebase following the > latest draft [1]. And I was actually surprised by the `mapfn` being > involved into the algorithm. > Have you tried es6-shim? > > I mean, from the performance perspective it's probably .. ok-ish.. but > from the API design perspective it feels like combining the actual > transformation of an iterable (or of an array-like) with the mapping, is > the "too much of responsibility" anti-pattern. Why not filter then as well? > (or, as one of the comments on a diff review: "I'm actually disappointed > it won't do my laundry as well :P"). > > It probably should be just: > > ``` > Array.from(...).map(mapfn); > ``` > > Unless I'm missing something, and there was a special reason to include > the mapping. > Yes: https://github.com/rwaldron/tc39-notes/blob/c61f48cea5f2339a1ec65ca89827c8cff170779b/es6/2013-01/jan-30.md#revising-the-array-subclassing-kind-issue Any subclass of array will want to produce a list of its own "kind", but .map returns an Array. This thread is also a dup of: https://mail.mozilla.org/pipermail/es-discuss/2013-June/031500.html Rick
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