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| From | Thomas 'PointedEars' Lahn <PointedEars@web.de> |
| Newsgroups | comp.lang.javascript |
| Subject | Re: Cloning an object |
| Date | Fri, 06 Jul 2018 00:24:09 +0200 |
| Organization | PointedEars Software (PES) |
| Lines | 112 |
| Message-ID | <4080533.LvFx2qVVIh@PointedEars.de> (permalink) |
| References | <aYCdnU3Tes0_oLbGnZ2dnUU7-LHNnZ2d@westnet.com.au> <1620852.VI2in3QvqR@PointedEars.de> <d9423a2c-3ca3-7571-6fa0-aca40b1c6d0f@PointedEars.de> <9909bfec-c6e7-2a4a-2a54-ec9f271691c8@PointedEars.de> <phdcst$1hro$1@csiph.com> <4395113.31r3eYUQgx@PointedEars.de> <phkj7m$2ugj$1@csiph.com> <506b67da-b086-3d0e-5985-d0f8214da432@PointedEars.de> <phloi4$kb2$1@csiph.com> |
| Reply-To | Thomas 'PointedEars' Lahn <cljs@PointedEars.de> |
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Cezary Tomczyk wrote:
> var o = {
> a: 1,
> b: [
> {
> test: 'test'
> }
> ]
> };
>
> var cloned = clone(o);
>
> o.b[0].test = 'something';
>
> expect(cloned.b[0].test).toBe('test');
>
> This test doesn't pass. Basically, modifications on original object
> should not modify cloned object.
The object referred to by “o.b[0]” is NOT part of the original object,
therefore if you do _not_ make a “deep copy”, then only the *reference
value* stored in the “b” property of the original object is cloned (copied).
Despite the syntax that suggests otherwise, ECMAScript objects are NOT like
that:
,---------------------------------.
: o : Object :
:---------------------------------:
: +a : number = 1 :
: ,-----------------------------. :
: : +b : Array : :
: : ,-------------------------. : :
: : : +0 : Object : : :
: : :-------------------------: : :
: : : +test : string = "test" : : :
: : `-------------------------' : :
: `-----------------------------' :
`---------------------------------'
But like this:
,-----------------.
o --> : : Object :
:--------------:--:
: +a : number = 1 : ,--------------.
: +b : Array -------> : : Array :
`-----------------' :--------------: ,-------------------------.
: +0 : Object ---> : : Object :
`--------------' :-------------------------:
: +test : string = "test" :
`-------------------------'
When you clone an object without making a “deep copy”, i.e. a *clone* of the
*objects* that the first object’s properties *refer to*, then the clone will
access the same objects:
,-----------------.
o --> : : Object :
:--------------:--:
: +a : number = 1 : ,------------.-.
: +b : Array -------> : : Array :
`-----------------' :--------------: ,-------------------------.
: +0 : Object ---> : : Object :
`--------------' :-------------------------:
^ : +test : string = "test" :
: `-------------------------'
:
,-----------------. :
cloned --> : : Object : :
:--------------:--: :
: +a : number = 1 : :
: +b : Array -----------'
`-----------------'
vs. (“deep copy”)
,-----------------.
o --> : : Object :
:--------------:--:
: +a : number = 1 : ,------------.-.
: +b : Array -------> : : Array :
`-----------------' :--------------: ,-------------------------.
: +0 : Object ---> : : Object :
`--------------' :-------------------------:
: +test : string = "test" :
`-------------------------'
,-----------------.
cloned --> : : Object :
:--------------:--:
: +a : number = 1 : ,------------.-.
: +b : Array -------> : : Array :
`-----------------' :--------------:
: +0 : Object -----.
`--------------' :
:
,-------------------------. :
: : Object :<-'
:-------------------------:
: +test : string = "test" :
`-------------------------'
This important difference is why I insist on saying “the object referred to
by” instead of just “object”, and only using shorthand terminology with
previous definition.
--
PointedEars
FAQ: <http://PointedEars.de/faq> | <http://PointedEars.de/es-matrix>
<https://github.com/PointedEars> | <http://PointedEars.de/wsvn/>
Twitter: @PointedEars2 | Please do not cc me./Bitte keine Kopien per E-Mail.
Back to comp.lang.javascript | Previous | Next — Previous in thread | Next in thread | Find similar | Unroll thread
Recording changes to an object Andrew Poulos <ap_prog@hotmail.com> - 2018-06-21 15:54 +1000
Re: Recording changes to an object Julio Di Egidio <julio@diegidio.name> - 2018-06-21 01:47 -0700
Re: Recording changes to an object Ben Bacarisse <ben.usenet@bsb.me.uk> - 2018-06-21 17:01 +0100
Re: Recording changes to an object Julio Di Egidio <julio@diegidio.name> - 2018-06-21 09:48 -0700
Re: Recording changes to an object John G Harris <niam@jghnorth.org.uk.invalid> - 2018-06-22 09:58 +0100
Re: Recording changes to an object Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2018-06-21 21:03 +0200
Re: Recording changes to an object Julio Di Egidio <julio@diegidio.name> - 2018-06-21 16:25 -0700
Re: Recording changes to an object Andrew Poulos <ap_prog@hotmail.com> - 2018-06-22 09:34 +1000
Re: Recording changes to an object Julio Di Egidio <julio@diegidio.name> - 2018-06-21 17:02 -0700
Re: Recording changes to an object Julio Di Egidio <julio@diegidio.name> - 2018-06-21 18:03 -0700
Re: Recording changes to an object John G Harris <niam@jghnorth.org.uk.invalid> - 2018-06-22 10:06 +0100
Re: Recording changes to an object Julio Di Egidio <julio@diegidio.name> - 2018-06-22 02:21 -0700
Re: Recording changes to an object John G Harris <niam@jghnorth.org.uk.invalid> - 2018-06-22 18:31 +0100
Re: Recording changes to an object Julio Di Egidio <julio@diegidio.name> - 2018-06-22 20:16 -0700
Re: Recording changes to an object Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2018-06-22 02:23 +0200
Re: Recording changes to an object Julio Di Egidio <julio@diegidio.name> - 2018-06-21 17:31 -0700
Re: Recording changes to an object Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2018-06-22 02:55 +0200
Re: Recording changes to an object Andrew Poulos <ap_prog@hotmail.com> - 2018-06-22 12:37 +1000
Re: Recording changes to an object Julio Di Egidio <julio@diegidio.name> - 2018-06-22 02:23 -0700
Re: Recording changes to an object Jake Jarvis <pig_in_shoes@yahoo.com> - 2018-06-22 14:35 +0200
Re: Recording changes to an object Julio Di Egidio <julio@diegidio.name> - 2018-06-22 05:57 -0700
Re: Recording changes to an object Mickey Finn <mfinn@gmail.com> - 2018-06-22 15:43 -0300
Re: Recording changes to an object Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2018-06-22 13:51 +0200
Re: Recording changes to an object Julio Di Egidio <julio@diegidio.name> - 2018-06-22 06:04 -0700
Re: Recording changes to an object John G Harris <niam@jghnorth.org.uk.invalid> - 2018-06-22 18:33 +0100
Re: Recording changes to an object Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2018-06-24 14:36 +0200
Re: Recording changes to an object "Mark-" <nospam@mapson.xyz> - 2018-06-24 13:56 +0000
Re: Recording changes to an object John G Harris <niam@jghnorth.org.uk.invalid> - 2018-06-25 10:06 +0100
Re: Recording changes to an object Jonas Thörnvall <jonas.thornvall@gmail.com> - 2018-06-25 02:40 -0700
Re: Recording changes to an object Jonas Thörnvall <jonas.thornvall@gmail.com> - 2018-06-25 02:47 -0700
Re: Recording changes to an object Jonas Thörnvall <jonas.thornvall@gmail.com> - 2018-06-25 02:51 -0700
Re: Recording changes to an object Jonas Thörnvall <jonas.thornvall@gmail.com> - 2018-06-25 02:54 -0700
Re: Recording changes to an object Jonas Thörnvall <jonas.thornvall@gmail.com> - 2018-06-25 02:58 -0700
Re: Recording changes to an object John G Harris <niam@jghnorth.org.uk.invalid> - 2018-06-25 19:26 +0100
Re: Recording changes to an object Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2018-06-30 19:47 +0200
Re: Recording changes to an object John G Harris <niam@jghnorth.org.uk.invalid> - 2018-07-01 10:56 +0100
Re: Recording changes to an object Andrew Poulos <ap_prog@hotmail.com> - 2018-06-23 17:19 +1000
Re: Recording changes to an object Julio Di Egidio <julio@diegidio.name> - 2018-06-23 00:51 -0700
Re: Recording changes to an object John G Harris <niam@jghnorth.org.uk.invalid> - 2018-06-23 11:27 +0100
Re: Recording changes to an object Andrew Poulos <ap_prog@hotmail.com> - 2018-06-23 20:59 +1000
Re: Recording changes to an object Julio Di Egidio <julio@diegidio.name> - 2018-06-23 05:51 -0700
Re: Recording changes to an object Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2018-06-30 19:43 +0200
Re: Recording changes to an object Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2018-07-01 15:22 +0200
Re: Recording changes to an object Cezary Tomczyk <cezary.tomczyk@gmail.com> - 2018-07-02 16:29 +0200
Cloning an object (was: Recording changes to an object) Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2018-07-04 23:25 +0200
Re: Cloning an object Cezary Tomczyk <cezary.tomczyk@gmail.com> - 2018-07-05 10:00 +0200
Re: Cloning an object Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2018-07-05 19:49 +0200
Re: Cloning an object Cezary Tomczyk <cezary.tomczyk@gmail.com> - 2018-07-05 20:37 +0200
Re: Cloning an object Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2018-07-05 23:35 +0200
Re: Cloning an object Cezary Tomczyk <cezary.tomczyk@gmail.com> - 2018-07-05 23:54 +0200
Re: Cloning an object Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2018-07-06 00:32 +0200
Re: Cloning an object Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2018-07-06 00:24 +0200
Re: Cloning an object John G Harris <niam@jghnorth.org.uk.invalid> - 2018-07-06 18:48 +0100
Re: Cloning an object Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2018-07-06 23:51 +0200
Re: Cloning an object John G Harris <niam@jghnorth.org.uk.invalid> - 2018-07-07 15:51 +0100
Re: Cloning an object Julio Di Egidio <julio@diegidio.name> - 2018-07-07 08:39 -0700
Re: Cloning an object John G Harris <niam@jghnorth.org.uk.invalid> - 2018-07-09 10:20 +0100
Re: Cloning an object Julio Di Egidio <julio@diegidio.name> - 2018-07-09 02:35 -0700
Re: Cloning an object Julio Di Egidio <julio@diegidio.name> - 2018-07-09 02:41 -0700
Re: Cloning an object Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2018-07-08 12:20 +0200
Re: Cloning an object John G Harris <niam@jghnorth.org.uk.invalid> - 2018-07-08 14:38 +0100
Re: Cloning an object Julio Di Egidio <julio@diegidio.name> - 2018-07-08 13:10 -0700
Re: Cloning an object John G Harris <niam@jghnorth.org.uk.invalid> - 2018-07-09 09:48 +0100
Re: Cloning an object Julio Di Egidio <julio@diegidio.name> - 2018-07-09 02:28 -0700
Re: Cloning an object Julio Di Egidio <julio@diegidio.name> - 2018-07-09 02:38 -0700
Re: Cloning an object John G Harris <niam@jghnorth.org.uk.invalid> - 2018-07-09 19:11 +0100
Re: Recording changes to an object "Michael Haufe (TNO)" <tno@thenewobjective.com> - 2018-07-02 21:01 -0700
Re: Recording changes to an object Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2018-07-05 00:32 +0200
Re: Recording changes to an object "Michael Haufe (TNO)" <tno@thenewobjective.com> - 2018-07-04 19:23 -0700
Re: Recording changes to an object Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2018-07-05 06:38 +0200
Re: Recording changes to an object "Michael Haufe (TNO)" <tno@thenewobjective.com> - 2018-07-04 23:21 -0700
Re: Recording changes to an object Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2018-07-05 09:25 +0200
Re: Recording changes to an object "Michael Haufe (TNO)" <tno@thenewobjective.com> - 2018-07-05 07:44 -0700
Re: Recording changes to an object Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2018-07-05 19:35 +0200
Re: Recording changes to an object "Michael Haufe (TNO)" <tno@thenewobjective.com> - 2018-07-06 12:59 -0700
Re: Recording changes to an object Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2018-07-06 23:22 +0200
Re: Recording changes to an object "Michael Haufe (TNO)" <tno@thenewobjective.com> - 2018-07-07 12:45 -0700
Re: Recording changes to an object Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2018-07-08 11:13 +0200
Re: Recording changes to an object Julio Di Egidio <julio@diegidio.name> - 2018-07-08 05:03 -0700
Re: Recording changes to an object "Michael Haufe (TNO)" <tno@thenewobjective.com> - 2018-07-08 13:42 -0700
Re: Recording changes to an object Julio Di Egidio <julio@diegidio.name> - 2018-07-08 13:46 -0700
Re: Recording changes to an object "Michael Haufe (TNO)" <tno@thenewobjective.com> - 2018-07-08 13:41 -0700
Re: Recording changes to an object Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2018-07-09 00:35 +0200
Re: Recording changes to an object "Michael Haufe (TNO)" <tno@thenewobjective.com> - 2018-07-10 01:03 -0700
Re: Recording changes to an object Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2018-07-10 20:50 +0200
Re: Recording changes to an object "Michael Haufe (TNO)" <tno@thenewobjective.com> - 2018-07-10 16:09 -0700
Re: Recording changes to an object "Michael Haufe (TNO)" <tno@thenewobjective.com> - 2018-06-21 15:09 -0700
Re: Recording changes to an object Julio Di Egidio <julio@diegidio.name> - 2018-06-21 16:30 -0700
Re: Recording changes to an object "Michael Haufe (TNO)" <tno@thenewobjective.com> - 2018-06-21 16:57 -0700
Re: Recording changes to an object Julio Di Egidio <julio@diegidio.name> - 2018-06-21 17:01 -0700
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