demonstrated here indeed: http://jsperf.com/array-extras-second-argument
on average, closures plus scope lookup looks always slower but I'll add more tests. On Tue, Oct 25, 2011 at 12:23 AM, Brendan Eich <bren...@mozilla.com> wrote: > On Oct 24, 2011, at 2:53 PM, Axel Rauschmayer wrote: > > > that = this: > > - Your point is that forEach() and map() have a second parameter that > allows you to hand in a value for "this", right? > > => I have yet to find a clear argument in favor or against using that > = this here. Both solutions have performance implications, both solutions > add an extra line. that = this has two extra tokens, but adding a second > argument looks awkward. > > We're talking about performance, not "looks". Passing trailing |this| > parameters to the Array extras avoids allocation (bound object or closure) > per extra application. > > /be
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