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Groups > comp.lang.javascript > #33235
| From | Cezary Tomczyk <cezary.tomczyk@gmail.com> |
|---|---|
| Newsgroups | comp.lang.javascript |
| Subject | Re: Object.defineProperties |
| Date | 2017-05-06 15:26 +0200 |
| Organization | csiph.com Internet News Service |
| Message-ID | <oekitc$2tgv$1@csiph.com> (permalink) |
| References | (1 earlier) <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> |
On 05/05/2017 20:11, Thomas 'PointedEars' Lahn wrote:
> Cezary Tomczyk wrote:
>
>> On 05/05/2017 18:14, Thomas 'PointedEars' Lahn wrote:
>>> Cezary Tomczyk wrote:
>> [...]
>>>> I use:
>>>>
>>>> function isTypeOf(obj, typeToCheck) {
>>>> if (arguments.length < 2) {
>>>> return false;
>>>> }
>>>> return Object.prototype.toString.call(obj).slice(8,
>>> ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
>>>> -1).toLowerCase() === typeToCheck.toLowerCase();
>>> ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
>>>> }
>>>>
>>>> which gives me more precisely a type of object.
>>> I hope you have optimized that somewhat.
>>
>> I can't find a reliable way at the moment. Perhaps I should combine few
>> methods, but that might be an overengineering.
>
> 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. :-)
>>>> The Object.defineProperties says about object, but function, array are
>>>> also objects. That's why:
>>>>
>>>> if (typeof obj !== 'object' || obj === null)
>>>> throw new TypeError('bad obj');
>>>>
>>>> looks like a bug to me.
>>> typeof [] === "object", so that is OK. (common misconception)
>>
>> In a sense of that [] is an object - yes, but I'd prefer to know that
>> tested object is in fact an Array type. Operator instanceof looks
>> promising, but I need to check it anyway.
>
> Array.isArray() exists (since ECMAScript Ed. 5). For general and own
> (array) types, I am using “instanceof” or “constructor”. Most of the time,
> though, duck typing instead (“quack” ;-)).
Ah, right, I forgot about Array.isArray() :)
Finally I rewrote it a bit:
var _toString = {}.toString;
function isTypeOf(obj, typeToCheck) {
var objectType;
if (arguments.length !== 2) {
return false;
}
objectType = typeof obj;
if (typeToCheck === 'array' && Array.isArray(obj)
|| typeToCheck === 'null' && objectType === 'object'
|| typeToCheck === 'object' && objectType === 'object'
|| typeToCheck === 'number' && objectType === 'number'
|| typeToCheck === 'string' && objectType === 'string'
|| typeToCheck === 'boolean' && objectType === 'boolean'
|| typeToCheck === 'undefined' && objectType === 'undefined'
|| typeToCheck === 'symbol' && objectType === 'symbol'
) {
return true;
}
return _toString.call(obj).slice(8, -1).toLowerCase() ===
typeToCheck.toLowerCase();
}
--
Cezary Tomczyk
http://www.ctomczyk.pl/
https://www.aslint.org/ - Accessibility validation tool
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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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