That is a self-invoking anonymous function.

Check out the W3C's explanation of a self-invoking function.

Function expressions can be made "self-invoking".

A self-invoking expression is invoked (started) automatically, without being called.

Function expressions will execute automatically if the expression is followed by ().

You cannot self-invoke a function declaration.

That is a self-invoking anonymous function.

Check out the W3Schools explanation of a self-invoking function.

Function expressions can be made "self-invoking".

A self-invoking expression is invoked (started) automatically, without being called.

Function expressions will execute automatically if the expression is followed by ().

You cannot self-invoke a function declaration.

That is a self-invoking anonymous function. This blog post does a good job explaining them and their usage:

http://blog.themeforest.net/tutorials/ask-jw-decoding-self-invoking-anonymous-functions/

That is a self-invoking anonymous function.

Check out the W3C's explanation of a self-invoking function.

Function expressions can be made "self-invoking".

A self-invoking expression is invoked (started) automatically, without being called.

Function expressions will execute automatically if the expression is followed by ().

You cannot self-invoke a function declaration.