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Re: Multiple image preload construct?

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Message-ID <3145125.oXMAan8fah@PointedEars.de> (permalink)
From Thomas 'PointedEars' Lahn <PointedEars@web.de>
Reply-To Thomas 'PointedEars' Lahn <usenet@PointedEars.de>
Organization PointedEars Software (PES)
Date Wed, 28 Aug 2013 11:04:07 +0200
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Subject Re: Multiple image preload construct?
Newsgroups comp.lang.javascript
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Xref csiph.com comp.lang.javascript:21076

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Thomas 'PointedEars' Lahn wrote:

> Ken wrote:
>>      function loadImages(imgs, callback) {
>> 
>>          var i = 0, img, count = imgs.length, result = [];
>> 
>>          /// create images
>>          for(; img = imgs[i]; i++) {
> 
> That is awful code style for array iteration, in probably every language
> of the C family.  Consider this instead:
> 
>   for (var i = 0, count = len = imgs.length; i < len; ++i)
>   {

Considered and rejected :)  This creates an “implied global”, “len” (a 
ReferenceError in strict mode).  It would have to be, for example

  var count;

  for (var i = 0, len = count = imgs.length; i < len; ++i)

to fix that.

  var count = 0;

  for (var i = 0, len = imgs.length; i < len; ++i)

and counting “count” up would work, too.  If order does not matter,

  var count;

  for (var i = count = imgs.length; i--;)

and counting “count” down is an optimization to consider.

(Even though there is no block scoping with “var”, it is useful to keep the 
declarations of variables that are only used in the loop close to the loop.)

-- 
PointedEars

Twitter: @PointedEars2
Please do not Cc: me. / Bitte keine Kopien per E-Mail.

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Thread

Multiple image preload construct? Tuxedo <tuxedo@mailinator.com> - 2013-08-27 16:32 +0200
  Re: Multiple image preload construct? Tuxedo <tuxedo@mailinator.com> - 2013-08-27 17:06 +0200
  Re: Multiple image preload construct? Danny <dann90038@gmail.com> - 2013-08-27 10:29 -0700
  Re: Multiple image preload construct? Ken <usenet-so@abdiassoftware.com> - 2013-08-27 13:32 -0500
    Re: Multiple image preload construct? Tuxedo <tuxedo@mailinator.com> - 2013-08-27 20:54 +0200
      Re: Multiple image preload construct? Ken <usenet-so@abdiassoftware.com> - 2013-08-27 18:19 -0500
        Re: Multiple image preload construct? Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2013-08-28 01:37 +0200
          Re: Multiple image preload construct? Ken <usenet-so@abdiassoftware.com> - 2013-08-27 18:47 -0500
    Re: Multiple image preload construct? Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2013-08-27 23:02 +0200
      Re: Multiple image preload construct? Cezary Tomczyk <cezary.tomczyk@gmail.com> - 2013-08-27 23:20 +0200
        Re: Multiple image preload construct? Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2013-08-28 01:27 +0200
          Re: Multiple image preload construct? Cezary Tomczyk <cezary.tomczyk@gmail.com> - 2013-08-29 03:56 +0200
            Re: Multiple image preload construct? Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2013-08-29 15:16 +0200
      Re: Multiple image preload construct? Ken <usenet-so@abdiassoftware.com> - 2013-08-27 18:43 -0500
        Re: Multiple image preload construct? Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2013-08-28 02:08 +0200
          Re: Multiple image preload construct? Ken <usenet-so@abdiassoftware.com> - 2013-08-27 19:49 -0500
            Re: Multiple image preload construct? Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2013-08-28 03:17 +0200
              Re: Multiple image preload construct? Ken <usenet-so@abdiassoftware.com> - 2013-08-27 20:35 -0500
                Re: Multiple image preload construct? Dr J R Stockton <reply1300@merlyn.demon.co.uk.invalid> - 2013-08-29 19:32 +0100
              Re: Multiple image preload construct? John Harris <niam@jghnorth.org.uk.invalid> - 2013-08-28 16:20 +0100
            Re: Multiple image preload construct? Andrew Poulos <ap_prog@hotmail.com> - 2013-08-28 11:21 +1000
              Re: Multiple image preload construct? Ken <usenet-so@abdiassoftware.com> - 2013-08-27 20:48 -0500
                Re: Multiple image preload construct? Andrew Poulos <ap_prog@hotmail.com> - 2013-08-28 13:43 +1000
                Re: Multiple image preload construct? John Harris <niam@jghnorth.org.uk.invalid> - 2013-08-29 10:00 +0100
                Re: Multiple image preload construct? Andrew Poulos <ap_prog@hotmail.com> - 2013-08-30 07:25 +1000
                Re: Multiple image preload construct? John Harris <niam@jghnorth.org.uk.invalid> - 2013-08-30 10:11 +0100
        Re: Multiple image preload construct? Christoph Michael Becker <cmbecker69@arcor.de> - 2013-08-28 02:17 +0200
          Re: Multiple image preload construct? Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2013-08-28 02:38 +0200
      Re: Multiple image preload construct? Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2013-08-28 11:04 +0200
      Re: Multiple image preload construct? John Harris <niam@jghnorth.org.uk.invalid> - 2013-08-28 16:26 +0100

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