Need help understanding Twitter bootstraps plugins (jQuery)

Question

I get all of the plugins code except for one line, and due to the way search engines work I cant actually search for my question.

The question is what in the hell is this:

(!function($) {/*....*/})(jQuery);

Why does it say !functions($)?? I'm guessing for the same effect of the $.noConflict() but isn't that why we just use (function($) {/*...*/})(jQuery); it just wraps the dollar sign to our function block. I am completely aware that I could be way off base here, I'm still intermediate in jQuery/js.

If someone could please enlighten me on the effect of the NOT operator before the function statement, i would greatly appreciate it.

Edit: It would appear that i overlooked bootstrap not having (!function($) ... ) but just being !function($)... but you guys helped me in realizing it is just an alternative to ()

@LightnessRacesinOrbit yea check it out http://twitter.github.com/bootstrap/assets/js/bootstrap-tooltip.js — dhazelett, Feb 06 '12 at 09:12
First result on Google for "exclamation mark function definition javascript" is.... — Lightness Races in Orbit, Feb 06 '12 at 09:12
possible duplicate of [What does the exclamation mark do before the function?](http://stackoverflow.com/questions/3755606/what-does-the-exclamation-mark-do-before-the-function) — Lightness Races in Orbit, Feb 06 '12 at 09:12
facepalm moment... i didnt even think to write it all the way out... thank you sir! — dhazelett, Feb 06 '12 at 09:14
http://stackoverflow.com/questions/7586870/in-javascript-what-is-the-advantage-of-function-over-function too — Lightness Races in Orbit, Feb 06 '12 at 09:14

score 4 · Accepted Answer · answered Feb 06 '12 at 09:29

So there a couple things going on here. Everything is being wrapped in an anonymous function that is executed right away. This is to create a scope for the library so that when the author declares functions and variables they are are not global by default.

With me so far. Ok next thing is the whole ($){...}(jQuery) thing. What is going on here is the author is passing the jQuery library into the anonymous wrapper function as a parameter called $. So in the scope of the anonymous function he can use $ to reference jQuery as you would expect. This is more of a best practices thing because 99% of the time jQuery is already defined as $ in the global scope, but its considered bad form to refer to global variables within a functions scope, and thus he / she passes it in as a parameter.

Still there? The exclamation mark: there is a rule in Javascript that states the first line of a program MUST be an expression (ie not a function declaration aka statement). By prepending the ! the author is turning the declaration into an expression (that returns false). In this case however I don't think the ! is actually required because the declaration is wrapped in () and executed right away. (A function call is an expression)

Indeed, it's already an expression; the `!` is redundant. It's an _alternative_ to wrapping the declaration in parens, but the author has done both for some reason. And I don't know what you're referring to when you talk about the first line of a program; indeed the vast majority of Javascript scripts I'm sure begin with statements. — Lightness Races in Orbit, Feb 06 '12 at 12:27

Need help understanding Twitter bootstraps plugins (jQuery)

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