Re: puzzled by example code using the logical OR

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From	Ben Bacarisse <ben.usenet@bsb.me.uk>
Newsgroups	comp.lang.javascript
Subject	Re: puzzled by example code using the logical OR
Date	Mon, 23 Feb 2015 21:57:55 +0000
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"Evertjan." <exxjxw.hannivoort@inter.nl.net> writes:

> JeffG <jeffgutsell@fuse.net> wrote on 23 feb 2015 in 
> comp.lang.javascript:
>
>> I've been looking at a discussion of creating objects that 
> are
>> containers of all related functions and vars. An example 
> first step is
>> as follows: ar AppSpace = AppSpace || {};
>> I don't see the purpose of "||". I would appreciate an 
> explanation since
>> I cannot get a response from the author. I thought the 
> logical OR only
>> returns true or false based on comparing two values or 
> expressions.
>
> Incorrect. That only happens if || compares boolean values.
>
> AppSpace = AppSpace || {};
>
> AppSpace is set to AppSpace [so effectivly remains so],
> unless AppSpace returns false or empty or 0 or undefined,
> then AppSpace is set to {}, an empty object.

It's false, the empty string, 0 (both +0 and -0), NaNs, undefined and
null that are considered false.  (It's common not to care about -0 and
NaNs, but null matters a bit more.)

-- 
Ben.

Thread

puzzled by example code using the logical OR JeffG <jeffgutsell@fuse.net> - 2015-02-23 11:20 -0800
  Re: puzzled by example code using the logical OR "Evertjan." <exxjxw.hannivoort@inter.nl.net> - 2015-02-23 21:57 +0100
    Re: puzzled by example code using the logical OR Ben Bacarisse <ben.usenet@bsb.me.uk> - 2015-02-23 21:57 +0000
      Re: puzzled by example code using the logical OR Denis McMahon <denismfmcmahon@gmail.com> - 2015-02-23 22:10 +0000
        Re: puzzled by example code using the logical OR Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2015-02-23 23:39 +0100
      Re: puzzled by example code using the logical OR Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2015-02-23 23:12 +0100
  Re: puzzled by example code using the logical OR Joao Rodrigues <groups_jr-1@yahoo.com.br> - 2015-02-23 23:09 -0300
    Re: puzzled by example code using the logical OR Joao Rodrigues <groups_jr-1@yahoo.com.br> - 2015-02-23 23:26 -0300

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