Path: csiph.com!news.swapon.de!weretis.net!feeder4.news.weretis.net!feeder5.news.weretis.net!news.solani.org!.POSTED!not-for-mail
From: Thomas 'PointedEars' Lahn <PointedEars@web.de>
Newsgroups: comp.lang.javascript
Subject: Re: Object.defineProperties
Date: Sat, 06 May 2017 22:21:59 +0200
Organization: PointedEars Software (PES)
Lines: 80
Message-ID: <1982276.iZASKD2KPV@PointedEars.de>
References: <oebtq0$2611$1@csiph.com> <objects-20170503082342@ram.dialup.fu-berlin.de> <oec3h1$2dav$1@csiph.com> <1943190.NgBsaNRSFp@PointedEars.de> <oeid9d$1ag1$1@csiph.com> <1592229.TLkxdtWsSY@PointedEars.de> <oekitc$2tgv$1@csiph.com> <2032926.ElGaqSPkdT@PointedEars.de> <oel4aa$9ml$1@csiph.com>
Reply-To: Thomas 'PointedEars' Lahn <cljs@PointedEars.de>
Mime-Version: 1.0
Content-Type: text/plain; charset="UTF-8"
Content-Transfer-Encoding: 8Bit
X-Trace: solani.org 1494102119 31170 eJwNx8ERACAIA7CVqEDRcVBk/xH08oorwRNGp3l/GXo1TeYAfi5K2FwLI7orT1MmYmM3h7AeDtgQyg== (6 May 2017 20:21:59 GMT)
X-Complaints-To: abuse@news.solani.org
NNTP-Posting-Date: Sat, 6 May 2017 20:21:59 +0000 (UTC)
User-Agent: KNode/4.14.2
Cancel-Lock: sha1:wHk0akskWd89BWcrsDr1luPhMc4=
X-Face: %i>XG-yXR'\"2P/C_aO%~;2o~?g0pPKmbOw^=NT`tprDEf++D.m7"}HW6.#=U:?2GGctkL,f89@H46O$ASoW&?s}.k+&.<b';Md8`dH6iqhT)6C^.Px|[=M@7=Ik[_w<%n1Up"LPQNu2m8|L!/3iby{-]A+#YE}Kl{Cw$\U!kD%K}\2jz"QQP6Uqr],./"?;=4v
X-NNTP-Posting-Host: eJwFwYEBwCAIA7CXmNB2ngMo/59gAufHVhAMDCa9u1ZeoIVrCnlEAmuOxSzuXzrOKvPcVXoevBD/
X-User-ID: eJwFwYEBwCAIA7CXqFCo5yiO/09YQk9kVyQzOJyw14Og1ocj0VTlKGnjLflKjUzxAQ5tr+s2q0ke6or9AxHfE5s=
Face: 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
Xref: csiph.com comp.lang.javascript:33240

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
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.