title: Does comparison to 'undefined` still does a global scope lookup?
body: <p>Accordigng to <a href="http://www.ecma-international.org/ecma-262/5.1/#sec-15.1.1.3" rel="nofollow">http://www.ecma-international.org/ecma-262/5.1/#sec-15.1.1.3</a> <code>undefined</code> can't no longer be redefined. </p>
  
  <p><strong>Does it imply that global lookup (to find if</strong> <code>undefined</code> <strong>was redefined) is not happening anymore?</strong></p>
  
  <p>Though, it does seem to be unnecessary now :)</p>
  
  <p><strong>UPDATE</strong>
  Of course the question is about the <code>strict</code> mode :) Thanks T.J.</p>