Le 26/12/2013 05:00, Rick Waldron a écrit :
>
> On Wed, Dec 25, 2013 at 7:33 PM, David Bruant
>
>     For the rationale, the wiki states [1]:
>     "There are many array-like objects in JS (arguments objects, DOM
>     NodeLists, arrays from separate windows, typed arrays) and no
>     simple way to convert one of these to an instance of Array in the
>     current window; this is the rationale behind a simple conversion
>     function (Array.from)."
>
>     I think that if all of these objects had a good default
>     @@iterable, there wouldn't be a need for the array-like part of
>     Array.from.
>     The "good default" most likely being based on .length, etc.
>
>
> The array-like part is for all of those objects that _won't_ have an 
> @@iterator, for one reason or another
I must have missed these reasons. No @@iterator also means these objects 
cannot be iterated with via for-of loops by default and I can't think of 
a good reason for that for any of the listed (arguments, NodeList, 
arrays from different windows, typed arrays).
Do you have a link to previous discussions on this topic or a summary if 
that can be explained quickly?

> and for useful shimming in ES5 runtimes.
Even if Array.from relies on @@iterator for runtimes with symbols, it 
doesn't prevent runtimes without symbols to embed the iterator logic in 
the Array.from source (which is exactly what your prolyfill does).

David
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://mail.mozilla.org/pipermail/es-discuss/attachments/20131226/39b5d412/attachment.html>

Le 26/12/2013 05:00, Rick Waldron a écrit :
> The array-like part is for all of those objects that _won't_ have an 
> `@@iterator`, for one reason or another

I must have missed these reasons. No `@@iterator` also means these objects 
cannot be iterated with via for-of loops by default and I can't think of 
a good reason for that for any of the listed (`arguments`, `NodeList`, 
arrays from different windows, typed arrays).
Do you have a link to previous discussions on this topic or a summary if 
that can be explained quickly?

> and for useful shimming in ES5 runtimes.

Even if `Array.from` relies on `@@iterator` for runtimes with symbols, it 
doesn't prevent runtimes without symbols to embed the iterator logic in 
the `Array.from` source (which is exactly what your prolyfill does).