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Groups > comp.lang.javascript > #10659
| From | Dr J R Stockton <reply1204@merlyn.demon.co.uk> |
|---|---|
| Newsgroups | comp.lang.javascript |
| Subject | Re: Comparing arraies |
| Date | 2012-01-27 21:07 +0000 |
| Organization | Home |
| Message-ID | <MS7MNAG2HxIPFw38@invalid.uk.co.demon.merlyn.invalid> (permalink) |
| References | <8dc6b834-cd20-47a5-a085-f4d5e4402c38@c13g2000yqk.googlegroups.com> <4f218d62$0$6578$9b4e6d93@newsspool3.arcor-online.net> <4f21dd07$0$28275$862e30e2@ngroups.net> |
In comp.lang.javascript message <4f21dd07$0$28275$862e30e2@ngroups.net>,
Thu, 26 Jan 2012 23:08:55, Denis McMahon <denismfmcmahon@gmail.com>
posted:
>On Thu, 26 Jan 2012 18:29:06 +0100, Martin Honnen wrote:
>
>> Archos wrote:
>>> How to know if 2 arraies are equal? I was expecting that it could be
>>> checked so:
>>>
>>>>>> var array1 = [1,2,3,4], array2 = [1,2,3,4]; if (array1 === array2) {
>>>>>> console.log("array1 and array2 are equal"); }
>>>
>>> Since the comparing of strings or integers works:
>>>
>>> var a = "2", b = "2";
>>> if (a === b) { console.log("a == b"); }
>>
>> No, for objects (and arrays are objects) the identity is checked, no
>> comparison of properties or elements is done. So with e.g.
>>
>> var a1, a2;
>>
>> a1 = a2 = [1, 2, 3, 4];
>>
>> a1 == a2
>>
>> you get true as the two variables hold references to the same array
>> object.
>>
>> If you want to compare the elements you will need to define and
>> implement your own comparison function I think
>
>It might be easier to compare two vars universally, assuming the JSON
>object is available, by:
>
>function are_identical(var1, var2) {
>return JSON.stringify(var1) === JSON.stringify(var2);
>}
>
>I think this would work for anything that can be stringified by the
>JSON.stringify() method.
Observe :
A = new Array(5)
B = new Array(6)
for which A[<anything>] = B[<anything>] = undefined; yet String(B) is
visibly longer than String(A).
Note : JSON.stringify(A) -> [null,null,null,null,null]
so JSON cannot tell a null from an undefined (in FF 9.0.1).
Consider
A = [1, [1, 1], 1]
B = [[1, 1], [1, 1]]
String() gives the same for each, but JSON can tell the difference.
But, in general, enough will be reliably known about the array contents
for String() to be safe.
--
(c) John Stockton, nr London, UK. ?@merlyn.demon.co.uk Turnpike 6.05 WinXP.
Web <http://www.merlyn.demon.co.uk/> - FAQ-type topics, acronyms, and links.
Command-prompt MiniTrue is useful for viewing/searching/altering files. Free,
DOS/Win/UNIX now 2.0.6; see <URL:http://www.merlyn.demon.co.uk/pc-links.htm>.
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Comparing arraies Archos <raul.san@sent.com> - 2012-01-26 07:23 -0800
Re: Comparing arraies Martin Honnen <mahotrash@yahoo.de> - 2012-01-26 18:29 +0100
Re: Comparing arraies Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2012-01-26 19:50 +0100
Re: Comparing arraies Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2012-01-26 19:54 +0100
Re: Comparing arraies John G Harris <john@nospam.demon.co.uk> - 2012-01-27 16:49 +0000
Re: Comparing arraies Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2012-01-27 18:41 +0100
Re: Comparing arraies John G Harris <john@nospam.demon.co.uk> - 2012-01-28 11:28 +0000
Re: Comparing arraies Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2012-01-28 21:17 +0100
Re: Comparing arraies John G Harris <john@nospam.demon.co.uk> - 2012-01-29 14:55 +0000
Re: Comparing arraies Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2012-01-29 17:13 +0100
Re: Comparing arraies John G Harris <john@nospam.demon.co.uk> - 2012-01-30 15:27 +0000
Re: Comparing arraies Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2012-01-30 19:03 +0100
Re: Comparing arraies John G Harris <john@nospam.demon.co.uk> - 2012-01-31 15:07 +0000
Re: Comparing arraies Dr J R Stockton <reply1205@merlyn.demon.co.uk> - 2012-01-31 18:51 +0000
Re: Comparing arraies "Michael Haufe (TNO)" <tno@thenewobjective.com> - 2012-01-30 12:01 -0800
Re: Comparing arraies John G Harris <john@nospam.demon.co.uk> - 2012-01-31 11:06 +0000
Re: Comparing arraies "Michael Haufe (TNO)" <tno@thenewobjective.com> - 2012-01-31 06:08 -0800
Re: Comparing arraies John G Harris <john@nospam.demon.co.uk> - 2012-01-31 16:08 +0000
Re: Comparing arraies "Michael Haufe (TNO)" <tno@thenewobjective.com> - 2012-01-31 18:32 -0800
Re: Comparing arraies John G Harris <john@nospam.demon.co.uk> - 2012-02-01 17:02 +0000
Re: Comparing arraies "Michael Haufe (TNO)" <tno@thenewobjective.com> - 2012-02-01 10:07 -0800
Re: Comparing arraies John G Harris <john@nospam.demon.co.uk> - 2012-02-02 15:10 +0000
Re: Comparing arraies "Michael Haufe (TNO)" <tno@thenewobjective.com> - 2012-02-02 11:16 -0800
Re: Comparing arraies John G Harris <john@nospam.demon.co.uk> - 2012-02-07 15:14 +0000
Re: Comparing arraies Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2012-02-01 21:45 +0100
Re: Comparing arraies "Michael Haufe (TNO)" <tno@thenewobjective.com> - 2012-02-01 13:07 -0800
Re: Comparing arraies Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2012-02-01 23:44 +0100
Re: Comparing arraies "Michael Haufe (TNO)" <tno@thenewobjective.com> - 2012-02-01 18:22 -0800
Re: Comparing arraies Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2012-02-02 23:09 +0100
Re: Comparing arraies Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2012-02-03 01:47 +0100
Re: Comparing arraies John G Harris <john@nospam.demon.co.uk> - 2012-02-04 10:34 +0000
Re: Comparing arraies Dr J R Stockton <reply1205@merlyn.demon.co.uk> - 2012-02-05 16:47 +0000
Re: Comparing arraies John G Harris <john@nospam.demon.co.uk> - 2012-02-06 15:21 +0000
Re: Comparing arraies "Michael Haufe (TNO)" <tno@thenewobjective.com> - 2012-02-04 23:37 -0800
Re: Comparing arraies Denis McMahon <denismfmcmahon@gmail.com> - 2012-01-26 23:08 +0000
Re: Comparing arraies Denis McMahon <denismfmcmahon@gmail.com> - 2012-01-27 01:42 +0000
Re: Comparing arraies Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2012-01-27 11:41 +0100
Re: Comparing arraies Gene Wirchenko <genew@ocis.net> - 2012-01-26 16:24 -0800
Re: Comparing arraies "Evertjan." <exjxw.hannivoort@interxnl.net> - 2012-01-27 08:50 +0000
Re: Comparing arraies Dr J R Stockton <reply1204@merlyn.demon.co.uk> - 2012-01-27 21:07 +0000
Re: Comparing arraies "Evertjan." <exjxw.hannivoort@interxnl.net> - 2012-01-28 13:45 +0000
Re: Comparing arraies "Michael Haufe (TNO)" <tno@thenewobjective.com> - 2012-01-26 16:21 -0800
Re: Comparing arraies Martin Honnen <mahotrash@yahoo.de> - 2012-01-27 16:00 +0100
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