On Nov 5, 2011, at 9:38 AM, Allen Wirfs-Brock wrote:
> In a similar vain, what is the value of r in:
>
> let [z,y,...r] = {0:0, 1:1, 2:2, length: 3, 3:3,4:4};
>
> should it be [2] or [2,3,4] (and if the latter how is that determined)?
The inspiration for ... in the past came from (among other sources) Successor
ML:
http://successor-ml.org/index.php?title=Functional_record_extension_and_row_capture
> It seems to me that [2] is the right answer
The issue with ... in an array destructuring pattern is different from the case
without. We have a choice, as you say. It's not obvious that doing a "get" of
'length' on the RHS (once per ...) is the right answer. It's plausible in my
view that ... captures all indexed properties (index as defined by ECMA-262).
/be
> and if that is the cause, consistency requires that for the first problem z
> gets the value undefined.
>
> Allen
>
> On Nov 5, 2011, at 9:28 AM, Allen Wirfs-Brock wrote:
>
>> In the following declaration, what should be the value of z?
>>
>> let [z,y,z] = {0:0, 1:1, length: 2, 2:2};
>>
>> should it be be 2 or undefined
>>
>> undefined might be reasonable because it is an array pattern, and the source
>> object is only has two "array-like" elements
>> 2 might be reasonable because the source object actually has a property
>> named "2"
>>
>> Which alternative will be least surprising to JS programmers?
>>
>> Allen
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>>
>
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