javascript, strange comparison operator
<blockquote>
  <p><strong>Possible Duplicate:</strong><br>
  <a href="http://stackoverflow.com/questions/359494/javascript-vs-does-it-matter-which-equal-operator-i-use">Javascript === vs == : Does it matter which &ldquo;equal&rdquo; operator I use?</a>  </p>
</blockquote>



<p>I've met "<strong>!==</strong>" strange comparison operator in source code of some chrome extension. Code snippet:</p>

<pre><code>function closedTab(id) {
   if (openedTabs[id] !== undefined) {
      openedTabs[id].time = timeNow(0);
      closedTabs.unshift(openedTabs[id]);
   }
}
</code></pre>

<p>This operator is not used just once, so there's should some meaning.</p>

<p>Is "<strong>!==</strong>" came from some JavaScript magic? Or it's just equivalent to usual "!="?
Thanks</p>
