what does ! mean before function() in JavaScript?
<blockquote>
  <p><strong>Possible Duplicate:</strong><br>
  <a href="http://stackoverflow.com/questions/8305915/function-vs-function">!function(){ }() vs (function(){ })()</a>  </p>
</blockquote>



<p>It is fairly standard common practice to write Js code like this:</p>

<pre><code>function ($) {
    ...
}(jQuery)
</code></pre>

<p>I saw somebody using an exclamation mark first: <code>! function($)...</code></p>

<p>What does it actually mean, and what is that good for?</p>

<p>Example from <a href="http://twitter.github.com/bootstrap/assets/js/application.js" rel="nofollow">Twitter Bootstrap</a> (code retrieved 2012-03-07): </p>

<pre><code>!function ($) {

  $(function(){
    ...
})

}(window.jQuery)
</code></pre>
