title: What is the when.js equivalent of Q.js's "done()"?
body: <p>In addition to <code>then()</code>, Q.js also has a <a href="https://github.com/kriskowal/q/wiki/API-Reference#promisedoneonfulfilled-onrejected-onprogress" rel="nofollow"><code>done()</code></a>. <code>done()</code> is usually called at the end of a promise chain, like this:</p>
  
  <pre><code>promise
  .then(callback)
  .then(callback)
  .done(callback);
  </code></pre>
  
  <p>This will catch any rejections that were not handled by the previous <code>then()</code>s, and it will handle any exceptions raised in <code>then()</code>'s callbacks.</p>
  
  <p>Is there something similar in <a href="https://github.com/cujojs/when" rel="nofollow">when.js</a>? How do you handle exceptions raised in callbacks? And what if you never register a rejection handler?</p>