jQuery and Twitter Bootstrap function explanation

Question

If you see the twitter's bootstrap application.js file that exists in all documents, you will notice something the following code:

!function( $ ) {
    ...
}( window.jQuery );

Could someone explain why this is the case for the first line of the code?

thanks

Answer 1

It's a self executing function:

!function(x){}(y)

x is the parameter of the function and y is the parameter you pass in the auto-call of that function.

! is just a visual guide that tells you at a glance that the function is self executing. Another common practice is to wrap it in parenthesis instead. (function(){}())