What does following a function with (jQuery, window, document); mean?

Question

I have the following plugin:

;(function($, window, document)
{
...
...

})(jQuery, window, document);

I can understand what the ; is for and also realize that $ is the jQuery but can someone explain why is the function followed by (jQuery, window, document);

score 11 · Accepted Answer · answered Oct 04 '12 at 09:22

11

It's called a 'self ivoking' or 'immediately invoked' function. It means that the function is run as soon as it is created using the parameters in the final set of brackets.

Further information

answered Oct 04 '12 at 09:22

Rory McCrossan

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what does that ; mean in ;(function ? – Ashok Raj Oct 04 '12 at 09:24
4

@AshokRaj That is likely a way to assure that any code that hasn't been properly closed, prior to the function, gets closed so that it doesn't interfere with this code. – Christofer Eliasson Oct 04 '12 at 09:31
nice thank you :) wouldn't this result in recursion ?? – Ashok Raj Oct 04 '12 at 09:33
@AshokRaj In what way do you think it would cause recursion? – Christofer Eliasson Oct 04 '12 at 09:52
i am sorry if wrong, but when the function itself is called at it's end, wouldn't that keep happening? – Ashok Raj Oct 04 '12 at 09:54
@AshokRaj no, it only occurs after the function is created. – Rory McCrossan Oct 04 '12 at 09:58
oh.awesome..there are a lot usability i didn't know.. – Ashok Raj Oct 04 '12 at 10:01

score 4 · Answer 2 · answered Oct 04 '12 at 09:31

This is called Immediately-Invoked Function Expression or Self-executing anonymous function. It enables the developer to hide his private declarations.

;(                                 // <---------------+
                                   //                 | encapsulate the function
  function($, window, document) {  // <--+ declare    | and call it passing three
                                   //    | anonymous  | arguments.
  }                                // <--+ function   |
                                   //                 |
)(jQuery, window, document);       // <---------------+

Christofer Eliasson · Answer 3 · 2012-10-04T09:31:33.837

I'm not sure I fully understand what you are asking, but what they do is that they pass the jQuery object, the window object and the document object to the function.

Most likely they do this for performance reasons. This makes it possible for a minimizer to shorten all the references to window and document to something like w and d, since it is local variables. In a large library, that could save a few bytes.

Additionally I believe (have no reference atm) that it is slightly faster to access a local variable, compared to a global variable (really a micro optimization though).

score 1 · Answer 4 · answered Oct 04 '12 at 09:22

1

It's an Immediately-Invoked Function Expression

That means, the function is declared and executed right away. This this done in order to create a new scope.

answered Oct 04 '12 at 09:22

Prinzhorn

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score 1 · Answer 5 · answered Oct 04 '12 at 09:22

1

It's an anonymous function that's immediately invoked (the so called IIFE).

The passing of jQuery aliases it to $, and window and document so they can be sure the reference is to the correct version in the outside environment.

answered Oct 04 '12 at 09:22

alex

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What does following a function with (jQuery, window, document); mean?

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