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Message-ID: <10328270.UdUkD2KWN8@PointedEars.de>
From: Thomas 'PointedEars' Lahn <PointedEars@web.de>
Reply-To: Thomas 'PointedEars' Lahn <cljs@PointedEars.de>
Organization: PointedEars Software (PES)
Date: Tue, 13 Mar 2012 20:54:09 +0100
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Subject: Re: FAQ Topic - What is (function(){ /*...*/ })() ? (2012-01-06)
Newsgroups: comp.lang.javascript
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J.R. wrote:

> J.R. wrote:
>> (function () {
>>   // ...
>> }());
>>
>> Notice the trailing semi-colon (;)
>>
> 
> Another way of doing the same is:
> 
> !function () {
>    // ...
> }();
> 
> It works because the logical NOT operator ( ! ) is telling the
> interpreter to treat function(){}() as an UnaryExpression, in
> conformance with ECMA-262 5th ed:
> 
> 11.4.9 Logical NOT Operator ( ! )
> The production UnaryExpression : ! UnaryExpression is evaluated as
> follows: 1. Let expr be the result of evaluating UnaryExpression.
> 2. Let oldValue be ToBoolean(GetValue(expr)).
> 3. If oldValue is true, return false.
> 4. Return true.
> 
> So the anonymous function expression will be called immediately after
> creation, and the result will be true.

The result of the /ExpressionStatement/ (and the program, if it is the last 
statement) will be `true' iff the function does not return a true-value.  
Otherwise it will be `false'.


PointedEars
-- 
Sometimes, what you learn is wrong. If those wrong ideas are close to the 
root of the knowledge tree you build on a particular subject, pruning the 
bad branches can sometimes cause the whole tree to collapse.
  -- Mike Duffy in cljs, <news:Xns9FB6521286DB8invalidcom@94.75.214.39>