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Re: Object.defineProperties

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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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