javascript anonymous function syntax variations

Question

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Location of parenthesis for auto-executing anonymous JavaScript functions?
Are “(function ( ) { } ) ( )” and “(function ( ) { } ( ) )” functionally equal in JavaScript?

I have seen the javascript anonymous functions written two different ways:

(function(){

})();

and

(function(){

}());

I have always thought the top one to be correct, and had never encountered the bottom one until now. I think this probably makes no difference at all but I thought I shoud be sure. Is there any difference between the two or are both ways equivalent?

score 2 · Accepted Answer · answered May 09 '12 at 10:55

2

They're equivalent.

The opening parenthesis is the important bit - it's the one that helps the parser figure out that what's coming is a function expression rather than a function declaration.

See http://kangax.github.com/nfe/ for an explanation of the difference.

answered May 09 '12 at 10:55

Alnitak

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Did I just have a déjà vu or have you answered a same question with this same answer – Esailija May 09 '12 at 11:00
@Esailija umm, if I did, I don't remember it... – Alnitak May 09 '12 at 11:01
2

lols, it's this one :D http://stackoverflow.com/questions/5938802/are-function-and-function-functionally-equal-i/5938902#5938902 I remember cos I upvoted you for it. It even has the same italics. – Esailija May 09 '12 at 11:04
2

@Esailija oh yeah :blush: You have a good memory - that answer was a year ago today! ;-) – Alnitak May 09 '12 at 11:06

Andreas Louv · Answer 2 · 2012-05-09T11:11:47.073

0

Oohh....... This was just for fun.....

~~They are equal, but use this shorted closure way instead: (Twitter uses it!)~~

!function(){

}();

You'll save many characters. 1 each time.

But I prefer to use this one that I think it's more readably:

(function(){

})();

than:

(function(){

}());

edited May 09 '12 at 11:11

answered May 09 '12 at 10:57

Andreas Louv

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4

Not necessarily easier to understand though... in general, I think it's better to use code minifiers. – Felix Kling May 09 '12 at 10:58
4

It is far more important for code to be obvious then it is for it to be short. – Quentin May 09 '12 at 10:59
1

no, don't use that way - it's not as easily recognised. – Alnitak May 09 '12 at 10:59
4

Do NOT use `!function...` it seriously hurts readability. And it doesn't matter if Twitter uses it or not. – Oleg May 09 '12 at 11:01
1

to be honest they all read the same to me, am I the only one who have developed a blind spot for this – Esailija May 09 '12 at 11:10

javascript anonymous function syntax variations

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