title: Why must Extends be the first property in a mootools class definition?
body: <p>The <a href="http://mootools.net/docs/core/Class/Class#Class%3aconstructor" rel="nofollow">mootools docs</a> state that "The Extends property should be the first property in a class definition.". After hours of investigation I stumbled upon this line in the mootools doc.</p>
  
  <p>Although my original problem could be solved after settings Extends as the first property I do not understand why.</p>
  
  <p>According to the js docs the order of properties in an object is subject of engine implementation. No guarantee of any kind is made about the order.</p>
  
  <p>So why does mootools rely on the order? Trying to read the mootools code did not help me ;).</p>