Uninteresting parameters

[Rick Waldron]

On Thu, Sep 29, 2011 at 12:09 AM, Rick Waldron <waldron.rick at gmail.com>wrote:

>
>
> On Wed, Sep 28, 2011 at 11:05 PM, Dean Landolt <dean at deanlandolt.com>wrote:
>
>>
>>
>> On Wed, Sep 28, 2011 at 10:06 PM, Mike Shaver <mike.shaver at gmail.com>wrote:
>>
>>> On Wed, Sep 28, 2011 at 9:11 PM, Brendan Eich <brendan at mozilla.com>
>>> wrote:
>>> > No worries, array extras are a great addition, we just need to keep
>>> rolling.
>>>
>>> Oh, no offense taken.  I just meant to say that there may be
>>> consistency-with-existing-pattern reasons to prefer one hole behaviour
>>> over another, is all.
>>>
>>
>>
>> Another reason to prefer the current hole-hopping behavior for array
>> extras is that it's currently the *only* way to get any efficiency
>> advantage sparse arrays. So regardless of rationale, it's strictly more
>> featureful and almost certainly the intended behavior if, as a developer,
>> you're aware of holes.
>>
>> But to reiterate the point I made earlier, in order for libraries to take
>> complete ownership of looping constructs we need a better way to detect
>> holes in userland -- something that can be optimized. I was trying to think
>> of a way to overload Array.prototype.indexOf and lastIndexOf but since we
>> don't have a type for holes this isn't really feasible (I'd thought of using
>> NaN as a sigil here as it's otherwise untestable in indexOf, but this would
>> be wrong on so many levels).
>>
>
> Holes can be detected and skipped by using the "in" operator...
>
> var array = [ 1, , 3, , 5 ];
>
> for ( var i = 0; i < array.length; i++ ) {
>  // Skip accessing in sparse arrays
> if ( i in array ) {
>  console.log( array[i] );
> }
> }
>
>
>
Sorry, that is to say you could do the reverse to detect and access their
index positions


>
>
>>  Regardless of where it goes (on Array, Array.prototype, or in a system
>> module), all we really need is something like a function that takes an index
>> and direction and returns the next hole's start index and length (or end
>> index). I'll put together a proposal if this isn't too controversial.
>>
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>>
>>
>
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