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    for...in

    There is a for each (variable in list) statement in Gecko 1.8a2. It is meant for E4X compatibility but seems to be available for all types of lists. Maybe this should be documented? --Wladimir Palant 08:00, 21 Jul 2005 (PDT)

    As of this writing the breadcrumbs output on this article is wrong. I filed bug 326770 regarding the issue. --Callek 20:33, 10 February 2006 (PST)

    sorted enumeration

    ECMA 262 says nothing about the order of for .. in's enumerated attributes being lexicographically sorted/ordered, but all versions of JS appear to do this sorting. I've seen code that relies on it. Worth a documentation note?

    note on use with arrays

    Callek writes:

    In my opinion, the Description covers the warning expressed in the added text.

    It does, but using for...in with arrays, and expecting it to return purely numeric indexes, is a common newbie mistake, and in my opinion warranted the more verbose note. So I'm restoring the note removed in the 11 February 2006 revision. --Tmetro 10:40, 20 September 2006 (PDT)

    mutating the array

    It might be worth a note that mutating the array (using Array.splice in my case) would exhibit the same behaviour one would see with a manual for loop - some elements get skipped / repeated / etc. Not going to do that myself with the recent posts in m.d.mdc about accidentally changing meaning though! :) --Mook 01:10, 24 December 2006 (PST)

    _Please_ make the change yourself. You can try getting a review from waldo or someone afterwards. If you don't make it, there's a high chance that no-one will. --Nickolay 07:35, 24 December 2006 (PST)
    I just made some changes which should hopefully address the mutation aspect. Feel free to say something here if you see improvements to my wording; I'm sure there are several which could be made, but I was trying not to be overly verbose. (Regarding hesitancy to make changes, I echo Nickolay -- make the change and post a request for review to the newsgroup, please.  :-) ) --Waldo 19:46, 6 January 2007 (PST)

    'never use on arrays'

    i assume this warning is obsolete now that with 1.7 array comprehension is actually encouraged, as seen here https://developer.mozilla.org/en/New_in_javascript_1.7#Array_comprehensions. i suggest just leaving this part:

    The for...in statement iterates over user-defined properties in addition to the array elements, so if you modify the array's non-integer or non-positive properties (e.g. by adding a "foo" property to it or even by adding a method or property to Array.prototype), the for...in statement will return the name of your user-defined properties in addition to the numeric indexes.

    similarly i would remove the Warning here https://developer.mozilla.org/en/Core_JavaScript_1.5_Reference/Statements/for...in#Description

    oberhamsi

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    Contributors to this page: Tmetro, oberhamsi, Nickolay, Callek, Dleonard, Waldo, Mook, Wladimir_Palant
    Last updated by: oberhamsi,