title: Invoke a callback at the end of a transition
body: <p>I need to make a FadeOut method (similar to jQuery) using <a href="http://d3js.org/">D3.js</a>. What I need to do is to set the opacity to 0 using <code>transition()</code>.</p>
  
  <pre><code>d3.select("#myid").transition().style("opacity", "0");
  </code></pre>
  
  <p>The problem is that I need a callback to realize when the transition has finished. How can I implement a callback?</p>