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Groups > comp.lang.javascript > #33240
| From | Thomas 'PointedEars' Lahn <PointedEars@web.de> |
|---|---|
| Newsgroups | comp.lang.javascript |
| Subject | Re: Object.defineProperties |
| Date | 2017-05-06 22:21 +0200 |
| Organization | PointedEars Software (PES) |
| Message-ID | <1982276.iZASKD2KPV@PointedEars.de> (permalink) |
| References | (4 earlier) <oeid9d$1ag1$1@csiph.com> <1592229.TLkxdtWsSY@PointedEars.de> <oekitc$2tgv$1@csiph.com> <2032926.ElGaqSPkdT@PointedEars.de> <oel4aa$9ml$1@csiph.com> |
Cezary Tomczyk wrote:
> On 06/05/2017 16:43, Thomas 'PointedEars' Lahn wrote:
>> Cezary Tomczyk wrote:
>>> On 05/05/2017 20:11, Thomas 'PointedEars' Lahn wrote:
>>>> To begin with, you should have
>>>>
>>>> var _toString = {}.toString;
>>>>
>>>> function isTypeOf(obj, typeToCheck) {
>>>> if (arguments.length < 2) {
>>>> return false;
>>>> }
>>>> return _toString.call(obj).slice(8, -1).toLowerCase() ===
>>>> typeToCheck.toLowerCase();
>>>> }
>>>
>>> Tiny optimisation, but that's fine. :-)
>>
>> Tiny optimization with big impact, I think. It saves
>>
>> - 1 lookup along the scope chain up to the global object for “Object”
>> *every time the function is called*
>>
>> - 2 lookups along the prototype chain each for “prototype” and
>> “toString”
>> *every time the function is called*
>>
>> and removes the dependency on a potentially non-initial value of
>> “Object.prototype” and “Object.prototype.toString”.
>
> That's true, but it is also important to mention that the impact is
> significant in case of hundred operations at the same time.
It is more significant if this function is called several times in a single-
threaded environment: the slower it is, the slower does the program run.
>>> Finally I rewrote it a bit:
>>> […]
>>> function isTypeOf(obj, typeToCheck) {
>>> […]
>>> if (arguments.length !== 2) {
>> This change does not make sense to me. “< 2” was clearer.
>
> Passing 1 argument doesn't make sense and that's why I've used !== 2.
Yes, but …
>>> return false;
>>> }
>>>
>>> objectType = typeof obj;
>> IMO, DRY demands declaration and initialization in one statement, if
>> possible.
>
> I did it on purpose. If argument will be !== 2 then it is not efficient
> to initialize anything before.
[Your reply here does not have anything to do with what you are replying
to.]
… why should the function return “false” if I pass 3 or more arguments to
it?
Besides, an insufficient number of arguments should throw an exception
instead.
>> The question remains: What is being *gained* by this comparably
>> inefficient precision instead of duck typing? _Not_ all things
>> that *can* be done also *should* be done.
>
> The gain is to get the real type (let me call it like that) of object.
Why is that important?
--
PointedEars
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Object.defineProperties Cezary Tomczyk <cezary.tomczyk@gmail.com> - 2017-05-03 08:36 +0200
Re: Object.defineProperties Cezary Tomczyk <cezary.tomczyk@gmail.com> - 2017-05-03 10:14 +0200
Re: Object.defineProperties Cezary Tomczyk <cezary.tomczyk@gmail.com> - 2017-05-03 10:59 +0200
Re: Object.defineProperties Cezary Tomczyk <cezary.tomczyk@gmail.com> - 2017-05-03 12:36 +0200
Re: Object.defineProperties Cezary Tomczyk <cezary.tomczyk@gmail.com> - 2017-05-03 18:47 +0200
Re: Object.defineProperties Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2017-05-05 18:18 +0200
Re: Object.defineProperties Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2017-05-05 18:14 +0200
Re: Object.defineProperties Cezary Tomczyk <cezary.tomczyk@gmail.com> - 2017-05-05 19:37 +0200
Re: Object.defineProperties Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2017-05-05 20:11 +0200
Re: Object.defineProperties Cezary Tomczyk <cezary.tomczyk@gmail.com> - 2017-05-06 15:26 +0200
Re: Object.defineProperties Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2017-05-06 16:43 +0200
Re: Object.defineProperties Cezary Tomczyk <cezary.tomczyk@gmail.com> - 2017-05-06 20:23 +0200
Re: Object.defineProperties Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2017-05-06 22:21 +0200
Re: Object.defineProperties Cezary Tomczyk <cezary.tomczyk@gmail.com> - 2017-05-06 23:19 +0200
Re: Object.defineProperties Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2017-05-07 02:40 +0200
Re: Object.defineProperties Stefan Weiss <krewecherl@gmail.com> - 2017-05-06 22:37 +0200
Re: Object.defineProperties Cezary Tomczyk <cezary.tomczyk@gmail.com> - 2017-05-06 23:05 +0200
Re: Object.defineProperties Stefan Weiss <krewecherl@gmail.com> - 2017-05-07 00:29 +0200
Re: Object.defineProperties Cezary Tomczyk <cezary.tomczyk@gmail.com> - 2017-05-07 10:06 +0200
Re: Object.defineProperties Stefan Weiss <krewecherl@gmail.com> - 2017-05-08 00:50 +0200
Re: Object.defineProperties Cezary Tomczyk <cezary.tomczyk@gmail.com> - 2017-05-08 13:17 +0200
Re: Object.defineProperties Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2017-05-07 02:37 +0200
Re: Object.defineProperties Cezary Tomczyk <cezary.tomczyk@gmail.com> - 2017-05-07 09:42 +0200
Re: Object.defineProperties Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2017-05-07 17:11 +0200
Re: Object.defineProperties Cezary Tomczyk <cezary.tomczyk@gmail.com> - 2017-05-07 20:08 +0200
Re: Object.defineProperties Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2017-05-05 20:59 +0200
Re: Object.defineProperties John G Harris <niam@jghnorth.org.uk.invalid> - 2017-05-06 10:35 +0100
Re: Object.defineProperties Cezary Tomczyk <cezary.tomczyk@gmail.com> - 2017-05-05 08:32 +0200
Re: Object.defineProperties Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2017-05-05 18:24 +0200
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