Re: What's wrong with this code?

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From	Thomas 'PointedEars' Lahn <PointedEars@web.de>
Newsgroups	comp.lang.javascript
Subject	Re: What's wrong with this code?
Date	Thu, 26 Feb 2015 16:04:21 +0100
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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.  An implementation that provided "null" for a primitive 
value or a reference to a native object would be non-conforming, which in 
*this* case means it is borken.

<http://www.ecma-international.org/publications/files/ECMA-ST-ARCH/ECMA-262,
%201st%20edition,%20June%201997.pdf#page=50>
<http://www.ecma-international.org/publications/files/ECMA-ST-ARCH/ECMA-262,
%202nd%20edition,%20August%201998.pdf#page=55>
<http://www.ecma-international.org/publications/files/ECMA-ST-ARCH/ECMA-262,
%203rd%20edition,%20December%201999.pdf#page=59>
<http://www.ecma-international.org/publications/files/ECMA-ST-ARCH/ECMA-262%205th%20edition%20December%202009.pdf#page=81>

-- 
PointedEars
FAQ: <http://PointedEars.de/faq> | SVN: <http://PointedEars.de/wsvn/>
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Thread

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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