Suggestion: Array.prototype.repeat

Herby Vojčík herby at mailbox.sk
Tue Jan 3 04:28:57 PST 2012


Hello,

binary ftw. See 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

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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