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Re: getElementsByClassName: BUG in JS-engine?

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Mattias Campe wrote:

> Op 18-11-12 12:09, Martin Honnen schreef:
>> Most DOM collections are "live" collections so it is difficult iterating
>> over them while manipulating them. Your loop manipulates the class of
>> elements and that way the collection changes while the loop is executed
>> and that leads to elements being skipped as after setting
>>    alleOpvallendeAlineas[0].className
>> that element is removed from the collection and the one that was at
>> index 1 is now at index 0. And the next loop iteration changes
>>    alleOpvallendeAlineas[1]
>> which is the third element in the original collection.
>>
>> One way to avoid that problem is working from the end of the collection
>> e.g.
>>    for (var l = alleOpvallendeAlineas.length, i = l - 1; i >= 0; i--) {
>>      alleOpvallendeAlineas[i].className = ...;
>>    }
> 
> I wouldn't have found that explanation myself, but it all makes sense,
> once you know that :). So it's not a bug in the JS-engine after all ;).

It could not have been a bug in "*the* JS-engine" because

1. There is no such thing.  Netscape/Mozilla JavaScript (e.g. in
   Mozilla-based browsers, NES compatibles, B2G, and Firefox OS) is but one
   of several ECMAScript implementations.  Other major implementations
   include JScript (e.g. in MSHTML/IE, with Windows Script Host, and on
   IIS), V8 (e.g. in Chromium/Google Chrome, on Android, and as base of
   node.js), Apple JavaScriptCore (e.g. in Safari, and on the iPhone/iPad),
   Opera ECMAScript (in Opera and Opera Mobile), and KDE JavaScript (e.g.
   in Konqueror):

   <http://PointedEars.de/es-matrix> (to be updated)

   Despite the historic name of the newsgroup, all of those implementations
   are on-topic here and in similar newsgroups in other Usenet hierarchies.

2. The feature you are using here is not part of any ECMAScript
   implementation to begin with, but of a language-independent DOM API.
   You are merely using an implementation of that with ECMAScript
   implementations:

   <https://developer.mozilla.org/en/docs/DOM>

   Scripting a DOM using an ECMAScript implementation is on-topic here as
   well.

That said, next time you should be slow(er) to declare something a bug 
without being sure, much less use the word "bug" that way in the message' 
Subject:

<http://www.catb.org/~esr/faqs/smart-questions.html>,
in particular
<http://www.catb.org/~esr/faqs/smart-questions.html#idp29846432>.


HTH

PointedEars
-- 
Danny Goodman's books are out of date and teach practices that are
positively harmful for cross-browser scripting.
  -- Richard Cornford, cljs, <cife6q$253$1$8300dec7@news.demon.co.uk> (2004)

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getElementsByClassName: BUG in JS-engine? Mattias Campe <mattiaspuntcampe@geeeemeil.com> - 2012-11-18 11:47 +0100
  Re: getElementsByClassName: BUG in JS-engine? Martin Honnen <mahotrash@yahoo.de> - 2012-11-18 12:09 +0100
    Re: getElementsByClassName: BUG in JS-engine? Mattias Campe <mattiaspuntcampe@geeeemeil.com> - 2012-11-18 14:56 +0100
      Re: getElementsByClassName: BUG in JS-engine? Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2012-11-18 18:43 +0100

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