Why does jQuery's animation extension "jQuery Color" 's closure function take an undefined value as it's second parameter?
<blockquote>
  <p><strong>Possible Duplicate:</strong><br>
  <a href="http://stackoverflow.com/questions/4650442/javascript-function-with-undefined-parameter">JavaScript function with ‘undefined’ parameter</a>  </p>
</blockquote>



<p>I'm looking the jQuery Color source code here</p>

<p><a href="http://code.jquery.com/color/jquery.color-2.1.0.js" rel="nofollow">http://code.jquery.com/color/jquery.color-2.1.0.js</a></p>

<p>And I found that the closure function take an undefined value as it's second parameter.
See below:</p>

<pre><code>(function( jQuery, undefined ) {

    var stepHooks = "backgroundColor borderBottomColor borderLeftColor borderRightColor borderTopColor color columnRuleColor outlineColor textDecorationColor textEmphasisColor",

    // plusequals test for += 100 -= 100
    rplusequals = /^([\-+])=\s*(\d+\.?\d*)/,
    // a set of RE's that can match strings and generate color tuples.
</code></pre>

<p>Or you can see it in the source code. Look at the second parameter.</p>

<p>The point I want to know is that why the second parameter is undefined?</p>

<p>I think it is an approach to strictly set the function to receive only one parameter.</p>

<p>I'm I right? Or anyone can help me out?</p>
