title: Javascript !undefined gives true?
body: <p>When I try to alert a negation of variable having <code>undefined</code> value , I get the output as true?</p>
  
  <pre><code>alert(undefined);
  alert(!undefined);
  </code></pre>
  
  <p>The first alert gives <code>undefined</code> and second alert gives <code>true</code>.
  Is this the expected behavior. If so then why ?Am I missing some concept/theory about <code>undefined</code> in Javascript?</p>