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Groups > comp.lang.javascript > #26939
| From | Ben Bacarisse <ben.usenet@bsb.me.uk> |
|---|---|
| Newsgroups | comp.lang.javascript |
| Subject | Re: What's wrong with this code? |
| Date | 2015-02-26 15:37 +0000 |
| Organization | A noiseless patient Spider |
| Message-ID | <87mw40n0or.fsf@bsb.me.uk> (permalink) |
| References | <b2751271-cbda-4bcd-9217-a37eb3fa58b0@googlegroups.com> <8761aopx65.fsf@bsb.me.uk> <2083952.afr504CXY5@PointedEars.de> |
Thomas 'PointedEars' Lahn <PointedEars@web.de> writes:
> Ben Bacarisse wrote:
>
>> denissavenok@gmail.com writes:
>>> The function doesn't work as expected. Why?
>>>
>>> var isUndefinedOrNull = function(obj) {
>>> return /^(?:undefined|null)$/.test(typeof obj);
>>> };
>>
>> If the type of obj is Null, typeof is defined to yield 'object'.
>>
>> You might (in some very odd implementation) get 'null' from typeof, but
>> that's only because the result is up to the implementation in some very
>> specific cases.
>
> To be exact, a conforming implementation of ECMAScript could only provide
> "null" as the result of a “typeof” operation if the operand was a reference
> to a host object.
To be more exact, only if the reference is to a host object that does
not implement [[Call]]. For references to callable object, both native
and host, the result must be 'function'.
<snip>
--
Ben.
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What's wrong with this code? denissavenok@gmail.com - 2015-02-26 01:18 -0800
Re: What's wrong with this code? Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2015-02-26 12:17 +0100
Re: What's wrong with this code? Ben Bacarisse <ben.usenet@bsb.me.uk> - 2015-02-26 14:25 +0000
Re: What's wrong with this code? Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2015-02-26 16:04 +0100
Re: What's wrong with this code? Ben Bacarisse <ben.usenet@bsb.me.uk> - 2015-02-26 15:37 +0000
Re: What's wrong with this code? Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2015-02-26 17:09 +0100
Re: What's wrong with this code? Joao Rodrigues <groups_jr-1@yahoo.com.br> - 2015-02-26 14:09 -0300
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