Why does Array.from accept non-iterable arraylikes?

Erik Arvidsson erik.arvidsson at gmail.com
Mon Jun 24 09:07:01 PDT 2013


I'm with Jason here.

The only argument I can vaguely remember is that people want to be
able to use these on old browsers without @@iterator? But I don't see
why a polyfill could not tag things with __iterator__ or something
else?

On Mon, Jun 24, 2013 at 11:54 AM, Jason Orendorff
<jason.orendorff at gmail.com> wrote:
> According to [1], Array.from will first try treating the argument as
> an iterable, then as an arraylike. This is much better than just
> arraylike. The committee considered making it iterable only, but
> decided against it. The rationale recorded in the notes is:
>
>     RW: No.
>
> Rick, can you expand on that a bit? :-)
>
> I propose changing it to iterable only. All builtin arraylike objects
> are iterable now, including arguments, per the same discussion.[1]
> Certainly the idea is for all DOM arraylikes to be iterable. So what
> is this for?
>
>   [1]: https://github.com/rwldrn/tc39-notes/blob/master/es6/2012-11/nov-29.md#revisit-nov-27-resolution-on-iterables-in-spread
>
> -j
>
> P.S. Rick: Thanks again for taking notes at the meetings. They're
> indispensible. I've cloned the repo; grepping the notes has been super
> useful too.
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-- 
erik


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