Re: FAQ Topic - What is (function(){ /.../ })() ? (2012-01-06)

Path	csiph.com!x330-a1.tempe.blueboxinc.net!usenet.pasdenom.info!aioe.org!.POSTED!not-for-mail
From	"J.R." <groups_jr-1@yahoo.com.br>
Newsgroups	comp.lang.javascript
Subject	Re: FAQ Topic - What is (function(){ /.../ })() ? (2012-01-06)
Date	Sun, 22 Jan 2012 07:10:52 -0200
Organization	Aioe.org NNTP Server
Lines	65
Message-ID	<jfgjqf$48c$1@speranza.aioe.org> (permalink)
References	<4f063989$0$283$14726298@news.sunsite.dk> <h0gqg7lji6327vo8eeiuv71urmrvger83q@4ax.com> <jel6t0$8v3$1@speranza.aioe.org>
NNTP-Posting-Host	edb3lPNLwDIT/BKKc/Xuzw.user.speranza.aioe.org
Mime-Version	1.0
Content-Type	text/plain; charset=ISO-8859-1; format=flowed
Content-Transfer-Encoding	7bit
X-Complaints-To	abuse@aioe.org
User-Agent	Mozilla/5.0 (Windows NT 6.0; rv:8.0) Gecko/20111105 Thunderbird/8.0
X-Antivirus-Status	Clean
X-Notice	Filtered by postfilter v. 0.8.2
X-Antivirus	avast! (VPS 120121-1, 01/21/2012), Outbound message
Xref	x330-a1.tempe.blueboxinc.net comp.lang.javascript:10465

Show key headers only | View raw

On 11/01/2012 21:44, J.R. wrote:
> On 11/01/2012 05:54, Hans-Georg Michna wrote:
>> On Fri, 06 Jan 2012 00:00:02 +0000, FAQ server wrote:
>>
>>> -----------------------------------------------------------------------
>>> FAQ Topic - What is (function(){ /*...*/ })() ?
>>> -----------------------------------------------------------------------
>>>
>>> This is an anonymous FunctionExpression that is called
>>> immediately after creation.
>>>
>>> Variables declared inside a function are not accessible from
>>> outside the function. This can be useful, for example, to hide
>>> implementation details or to avoid polluting the global scope.
>>>
>>> <URL: http://yura.thinkweb2.com/named-function-expressions/>
>>> <URL: http://jibbering.com/faq/notes/closures/>
>>> <URL:
>>> http://dmitrysoshnikov.com/ecmascript/chapter-5-functions/#question-about-surrounding-parentheses>
>>>
>>>
>>>
>>> The complete comp.lang.javascript FAQ is at
>>> http://jibbering.com/faq/
>>
>> It may be a good idea to mention that it is sometimes written
>> as:
>>
>> (function(){ /*...*/ }())
>>
>> Note the different arrangement of the last parentheses.
>>
>> I believe this is functionally equivalent.
>
> Besides, JSLint complains about any different form other than this:
>
> (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.

-- 
Joao Rodrigues (J.R.)

Thread

FAQ Topic - What is (function(){ /*...*/ })() ? (2012-01-06) "FAQ server" <javascript@dotinternet.be> - 2012-01-06 00:00 +0000
  Re: FAQ Topic - What is (function(){ /*...*/ })() ? (2012-01-06) Hans-Georg Michna <hans-georgNoEmailPlease@michna.com> - 2012-01-11 08:54 +0100
    Re: FAQ Topic - What is (function(){ /*...*/ })() ? (2012-01-06) "J.R." <groups_jr-1@yahoo.com.br> - 2012-01-11 21:44 -0200
      Re: FAQ Topic - What is (function(){ /*...*/ })() ? (2012-01-06) Hans-Georg Michna <hans-georgNoEmailPlease@michna.com> - 2012-01-12 09:26 +0100
      Re: FAQ Topic - What is (function(){ /*...*/ })() ? (2012-01-06) "J.R." <groups_jr-1@yahoo.com.br> - 2012-01-22 07:10 -0200
        Re: FAQ Topic - What is (function(){ /*...*/ })() ? (2012-01-06) Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2012-03-13 20:54 +0100

csiph-web