What does $([]) mean in jQuery?
<pre><code>var username = $("#username"),
                password = $("#password"),
                allFields = $([]).add(username).add(password);
</code></pre>

<p>What is allFields?  What is $([])? </p>

<p>Being a newbie to Javascript/jQuery, I've never seen this $([]) notation before and I'm interested in its associated methods.  </p>

<p>Given that its "$([])", it's tricky to search for.  And a Google search of arrays in Javascript (guessing that thing is an array of some sort) yields the typical arrays I'm familiar seeing.</p>

<p>So what is $([])?  Can anyone point me to some documentation?  I'm interested in learning how to use this strange thing.</p>
