It's usually to namespace (see later) and control the visibility of member functions and/or variables. Think of it like an object definition. jQuery plugins are usually written like this.
function globalFunction() {
var localFunction1 = function() {
//I'm anonymous! But localFunction1 is a reference to me!
};
function localFunction2() {
//I'm named!
}
}
In the above scenario, you can call globalFunction() from anywhere, but you cannot call localFunction1 or localFunction2.
What you're doing when you write (function() { ... code ... })(), is you're making the code inside a function literal (meaning the whole "object" is actually a function). After that, you're self-invoking the function (the final ()). So the major advantage of this as I mentioned before, is that you can have private methods/functions and properties:
(function() {
var private_var;
function private_function() {
//code
}
})()
The neat thing is that you can also define things inside and expose it to the outside world so (an example of namespacing so you can basically create your own library/plugin):
var myPlugin = (function() {
var private_var;
function private_function() {
}
return {
public_function1: function() {
},
public_function2: function() {
}
}
})()
http://stackoverflow.com/questions/2421911/what-is-the-purpose-of-wrapping-whole-javascript-files-in-anonymous-functions-li
