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Groups > comp.lang.javascript > #34150

Re: Iterating through an array (special syntax)

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Am 19.10.2017 um 21:53 schrieb Thomas 'PointedEars' Lahn:
...
> 
> Unless oldItems.length changes,
> 
>    for (var i=0, len = oldItems.length; i < len; i++) {
> 
> is more efficient.

Are you sure? I see no much differences (at least with nodejs 8):
#=================================================
#!/usr/bin/env node

var arr = [];
for(var i=0; i<5E7; i++) arr.push(i);

var x, start;

start = new Date().getTime();
for (var i=0; i<arr.length; i++) {};
console.log('A: ' + (new Date().getTime()-start) + ' ms');
start = new Date().getTime();
for (var i=0, len = arr.length; i < len; i++) {};
console.log('B: ' + (new Date().getTime()-start) + ' ms');
#=================================================

> 
>>           fn_each(oldItems[i], newItems[i]);
>>         }
> 
> This loop is pointlessly inefficient in any case.  You are already using
> Array.prototype.map(), thereby iterating through the array, so you can
> either output or accumulate the old and new value *in the callback*.

Ok.

I will think about your Promise solution. Thanks for your explanation.

...Rolf

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Thread

Iterating through an array (special syntax) Rolf Niepraschk <Rolf.Niepraschk@gmx.de> - 2017-10-17 12:39 +0200
  Re: Iterating through an array (special syntax) "Michael Haufe (TNO)" <tno@thenewobjective.com> - 2017-10-17 05:54 -0700
    Re: Iterating through an array (special syntax) Rolf Niepraschk <Rolf.Niepraschk@gmx.de> - 2017-10-17 15:03 +0200
      Re: Iterating through an array (special syntax) "Michael Haufe (TNO)" <tno@thenewobjective.com> - 2017-10-17 06:19 -0700
        Re: Iterating through an array (special syntax) Rolf Niepraschk <Rolf.Niepraschk@gmx.de> - 2017-10-17 18:46 +0200
          Re: Iterating through an array (special syntax) Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2017-10-18 13:55 +0200
            Re: Iterating through an array (special syntax) Rolf Niepraschk <Rolf.Niepraschk@gmx.de> - 2017-10-18 14:25 +0200
              Re: Iterating through an array (special syntax) "Evertjan." <exxjxw.hannivoort@inter.nl.net> - 2017-10-18 15:38 +0200
              Re: Iterating through an array (special syntax) Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2017-10-18 15:49 +0200
          Re: Iterating through an array (special syntax) "Michael Haufe (TNO)" <tno@thenewobjective.com> - 2017-10-18 16:25 -0700
            Re: Iterating through an array (special syntax) Rolf Niepraschk <Rolf.Niepraschk@gmx.de> - 2017-10-19 07:50 +0200
            Re: Iterating through an array (special syntax) Rolf Niepraschk <Rolf.Niepraschk@gmx.de> - 2017-10-19 15:15 +0200
              Re: Iterating through an array (special syntax) Julio Di Egidio <julio@diegidio.name> - 2017-10-19 06:36 -0700
                Re: Iterating through an array (special syntax) Julio Di Egidio <julio@diegidio.name> - 2017-10-19 06:39 -0700
                Re: Iterating through an array (special syntax) Rolf Niepraschk <Rolf.Niepraschk@gmx.de> - 2017-10-19 18:16 +0200
                Re: Iterating through an array (special syntax) Julio Di Egidio <julio@diegidio.name> - 2017-10-19 18:55 -0700
              Re: Iterating through an array (special syntax) Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2017-10-19 21:53 +0200
                Re: Iterating through an array (special syntax) Rolf Niepraschk <Rolf.Niepraschk@gmx.de> - 2017-10-20 07:55 +0200
                Re: Iterating through an array (special syntax) Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2017-10-20 21:48 +0200
  Re: Iterating through an array (special syntax) Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2017-10-18 04:50 +0200

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