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From Christopher Lenz <cml...@gmx.de>
Subject Re: null
Date Thu, 08 Jan 2009 14:01:21 GMT
On 08.01.2009, at 14:37, Sven Helmberger wrote:
> Noah Slater schrieb:
>> On Thu, Jan 08, 2009 at 02:21:27PM +0100, Sven Helmberger wrote:
>>> Shouldn't couchdb treat null and undefined values the same?
>> Well, a "null" value is a way of saying "this doesn't have a value"  
>> but when
>> something is undefined, you don't know if it has a value or not.  
>> The difference
>> is subtle, but it's an important one.
>>> I am aware that there is in fact a difference in javascript, but  
>>> since
>>> there is no "undefined" keyword for JSON, I would argue that that  
>>> should
>>> not be the case for JSON and couchdb.
>> Well, an undefined value is by definition, undefined.
>
> in javascript, "undefined" is a keyword for an undefined value.  
> exactly the value that doc._rev has when doc has no property _rev.

Technically, and nitpickingly, that's not the value doc._rev has,  
because doc._rev does not exist ;) It's the value returned by  
Javascript when you access a property that doesn't exist.

> The absence of an "undefined" keyword leads me to the expectation  
> that for JSON {} should be the same as {"foo":null}.

No, "undefined" means that an object has no such property, whereas  
{"foo":null} clearly *has* a "foo" property.

I'm not sure what problem you're trying to solve here. If you need to  
state that a JSON object doesn't have a property, simply omit it. No  
need for an invalid keyword.

Also note that "invalid" is not a keyword in Javascript either, it's  
the string value returned by `typeof somethingUndefined`.

Cheers,
--
Christopher Lenz
   cmlenz at gmx.de
   http://www.cmlenz.net/


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