title: Why does this event handler use "e = e || event"?
body: <p>Can someone explain me what does this line of code means:</p>
  
  <pre><code>function(e) { e = e || event; e.returnValue = false; return false; }
  </code></pre>
  
  <p>Why is the parameter named <code>e</code>?<br>
  If I change it to 'myparam' will it work?<br>
  What does <code>e = e</code> mean?</p>
  
  <p>Where is the variable <code>event</code> ( after <code>||</code> ) declared ?
  What is <code>e.returnValue?</code></p>