Suggestion: Array.prototype.repeat

Nadav Shesek nadav at shesek.info
Tue Jan 3 10:52:15 PST 2012


Sorry - I had my email address misconfigured so it rejected my email.
Sending it again:


> Added my own repeatF() to the tests at http://jsperf.com/array-repeat/6.
> Seems to be much faster than the others, at least on V8.
>
>
> On Tue, Jan 3, 2012 at 2:28 PM, Herby Vojčík <herby at mailbox.sk> wrote:
>
>
>  Hello,
>>
>>>
>> binary ftw. See http://jsperf.com/array-**repeat/4<http://jsperf.com/array-repeat/4>Array.prototype.repeatD.
>>
>> And I also tried push.apply in repeatC (not to copy over the array using
>> concat but grow it in place until possible) and it really surprised me it
>> was that much slower. Concat is probably heavily optimized.
>>
>>>
>> Herby
>>
>>>
>> -----Pôvodná správa----- From: Rick Waldron
>>
>> Sent: Tuesday, January 03, 2012 2:21 AM
>>
>> To: Adam Shannon
>>
>> Cc: es-discuss at mozilla.org ; Mariusz Nowak
>>
>> Subject: Re: Suggestion: Array.prototype.repeat
>>
>>
>>
>>
>>
>> On Mon, Jan 2, 2012 at 5:55 PM, Adam Shannon <adam at ashannon.us> wrote:
>> Another thing to think about is that .repeat (both on String and
>> Array) will be used a lot in production. So it would make sense for
>> each solution to be optimized for their specific case. It doesn't make
>> sense to slow down something as trivial as .repeat()
>>
>>
>> Creating a 10000 item array by repeating a 1000 item array 10 times, the
>> difference is negligible when compared the implementation that I wrote, not
>> the one given above
>>
>> http://jsperf.com/array-**repeat/2 <http://jsperf.com/array-repeat/2>
>>
>> Also, note that I had to "make up" my own Array.repeat() because the
>> Array.generate shown above did not create the same return as the initial
>> Array.prototype.repeat(), but I stuck to the concepts laid out - no new
>> array is initialized (except that Array.prototype.slice _does_ initialize a
>> new Array() ).
>>
>> Rick
>>
>>
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>
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