 <code>source</code>. Taken from
underscore.js.</p>            </td>
            <td class="code">
              <div class="highlight"><pre><span class="kd">function</span> <span class="nx">extend</span><span class="p">(</span><span class="nx">obj</span><span class="p">,</span> <span class="nx">source</span><span class="p">)</span> <span class="p">{</span>
  <span class="k">for</span> <span class="p">(</span><span class="kd">var</span> <span class="nx">prop</span> <span class="k">in</span> <span class="nx"