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From: Ben Bacarisse <ben.usenet@bsb.me.uk>
Newsgroups: comp.lang.javascript
Subject: Re: What's wrong with this code?
Date: Thu, 26 Feb 2015 15:37:40 +0000
Organization: A noiseless patient Spider
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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.