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| From | Thomas 'PointedEars' Lahn <PointedEars@web.de> |
| Newsgroups | comp.lang.javascript |
| Subject | Re: Save instance of array "undo" and copy it back to array. |
| Date | Sat, 18 Mar 2017 15:01:08 +0100 |
| Organization | PointedEars Software (PES) |
| Lines | 69 |
| Message-ID | <1968884.iZASKD2KPV@PointedEars.de> (permalink) |
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| Reply-To | Thomas 'PointedEars' Lahn <cljs@PointedEars.de> |
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JJ wrote: > On Fri, 17 Mar 2017 02:00:39 -0700 (PDT), jonas.thornvall@gmail.com wrote: >> If not, how would one go on calculate it? > > It depends on what type of values are stored in each array element. Most certainly not. The values referred by array elements are most certainly _not_ part of the memory required for storing the array. An efficient implementation would store pointers in the array only. > - Boolean type only need one byte but is rounded up to either 32-bit or > 64-bit integer [1]. No, it depends on the implementation of ECMAScript. > - Number type is a 64-bit floating point number. At minimum, to satisfy IEEE 754 requirements. > - String type is either a 32-bit or 64-bit integer [1] which is a memory > pointer pointing to the actual UTF-8 string data. i.e. it has two data: > pointer & text. Again, that depends on the implementation. > - Date type is […] > - Object and Array types are […] > - Function type is […] See above. > […] a structure array […] Another figment of your vivid imagination. > depending on the JavaScript engine. Not “JavaScript engine”, but _implementation of ECMAScript_. The various languages whose name contains “JavaScript” are _not_ the only implementations of ECMAScript. You have been told this before ad nauseam. Will you *ever* learn? > In your example code, the operation would be the assignment of the array > element. Which is _not_ a “variable assignment”, but a property-write access. > Since undoing a variable assignment requires you to know the > original variable value, you'll need to store the original value before > the variable assignment is actually performed. I'd recommend using the > `Object.watch()` to do this. Even your half-knowledge is out of date. Object.*prototype*.watch() is proprietary (implementation-dependent, precisely SpiderMonkey-only), intended for *debugging*, and is deprecated (in favor of getters/setters and/or Proxy, I presume). Object.observe(), which you might have meant instead, is proprietary, and deprecated in favor of getters/setters and/or Proxy, too. <https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/watch> pp. -- 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.
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Save instance of array "undo" and copy it back to array. jonas.thornvall@gmail.com - 2017-03-17 02:00 -0700
Re: Save instance of array "undo" and copy it back to array. JJ <jj4public@vfemail.net> - 2017-03-18 18:53 +0700
Re: Save instance of array "undo" and copy it back to array. Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2017-03-18 15:01 +0100
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