what exacly is (function()).()

Question

I'm a beginner in programming and I just wonder about one thing. To be exact the syntax of (function(){...}).()

This question has been probably asked but as I don't know what it is and how to call it, I had very small luck finding anything about this topic.

I have been checking some scripts lately and I noticed that in some of them people use:

(function(){
   ...
}).(something) //

So far I'm guessing it's something like function which calls itself right away? How do we use it and what are the advantages of this. What do I put inside where 'something' is? also sometimes before it starts it also has $ sign.

It's normally encountered as shorthand for the jQuery ready() event http://api.jquery.com/ready/ — Matthew Lock, Oct 30 '13 at 03:37
Is there a dot between the close and open parens? `(function(){...}).()` or `(function(){...})()` ? — SheetJS, Oct 30 '13 at 03:44

score 1 · Answer 1 · edited Feb 19 '14 at 13:05

1

Your first example is an anonymous self-invoked function. So you are right, it calls itself straight away. If it had a name, that name would ONLY be visible inside those brackets (..).

The dollar-sign functions are short-hand for jQuery calls.

edited Feb 19 '14 at 13:05

Qantas 94 Heavy

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answered Oct 30 '13 at 03:38

Samuel O'Malley

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score 1 · Accepted Answer · answered Oct 30 '13 at 03:41

1

Imagine a normal function:

function foo(){
    ...
}

Now let's call that function:

foo();

Instead of calling the function using its name, let's call it directly:

(function foo(){
    ...
})();

Since I don't use this function any where else, let's remove its name:

(function(){
    ...
})();

Want to pass a parameter to the function? Sure!

(function(something){
    ...
})(something);

Advantage of this? We have a scope!

(function(something){
    var bar = 5; // Can't access this outside the function
})(something);

This allows you to define stuff outside of the global scope.

answered Oct 30 '13 at 03:41

Vic

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thanks! answered all my questions and more :) appreciate that mate. – Tomasz Golinski Oct 30 '13 at 03:55
Vic has explained accurately. If you want to explore more visit [JavaScript Module Pattern: In-Depth](http://www.adequatelygood.com/JavaScript-Module-Pattern-In-Depth.html) – Mozak Oct 30 '13 at 04:29

score 0 · Answer 3 · answered Oct 30 '13 at 03:37

0

You are correct in that it a function that calls itself immediately, also called a self executing function.

The $ is just shorthand using jquery.

answered Oct 30 '13 at 03:37

Jeff Storey

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score 0 · Answer 4 · answered Oct 30 '13 at 03:39

function(){} is declaring a function, while when we do

$(function() {}) it means we pass a function into another function $() as parameter, where this function will be executed by $() when the times met

it is much like

var a = function() { do something }
a();

will do something, in C# its like delegate, while in C++ it is like function pointer, in javascript it is made simple though where you can directly embed a function at the position where a parameter should be

what exacly is (function()).()

4 Answers4