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in the last few days i'm interesting in anonymous function in javascript , so i started to "explore" frameworks such as jquery , in the very first line i saw this piece of code :

var jQuery = (function() { .. functions .. }();

and a question came in mind - what is the purpose of that code? why a variable contain anonymous function? what is the uses with that var? is it kind of function container or something? if it is how to access the functions?

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  • Not really sure what you want to know. It is assigning the return value of the immediate function to jQuery. Most of the time you have this to isolate variables (scope). Immediate functions don't have to be anonymous btw. Commented Oct 16, 2011 at 15:46
  • related: stackoverflow.com/questions/4806150/… Commented Oct 16, 2011 at 15:47
  • It's called the module pattern. It's used to create a namespace. Commented Oct 16, 2011 at 15:48
  • You might want to read this. Commented Oct 16, 2011 at 15:51
  • Recommended read: adequatelygood.com/2010/3/JavaScript-Module-Pattern-In-Depth Commented Oct 16, 2011 at 16:03

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what is the purpose of that code?

You are actually missing a closing parenthesis for this code to be valid javascript:

var jQuery = (function() { ... })();

It defines an anonymous function and executes it immediately storing the result of it in the variable.

You can think of it like this:

var jQuery = foo();

It's just that they didn't bother to define foo as an external function as they didn't need to call it elsewhere in the code. So they defined it as an anonymous function.

By doing this everything that is declared inside this anonymous function is scoped and accessible only to the containing anonymous function. It is not accessible to the outside.

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Explain him the namespace pollution problem :-)
in case i have only functions inside this anonymous function , how to access those functions?
@MorSela, where do you want to access them? Normally everything that is inside this anonymous function is not accessible to the outside. It's scoped only inside this anonymous function.
@Mor Sela you cannot access the functions inside the anonymous function unless it returns a value that explicitly exposes them.
@Mor You assign them as properties to an object which you then return from the anonymous function.
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By reducing scope for all contents of the function, you prevent possible collisions in the global scope, accidental hoisting, and minimize the additional attached objects to the window object.

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