title: d3 select anything with a specific class
body: <p>I am trying to select all elements with a certain class. They might have different classes before, or after this class, but as long as they have this class they should be selected</p>
  
  <p>ex:</p>
  
  <pre><code>&lt;g class="class a, class b, class c"&gt;
  &lt;g class="class q, class r, class z"&gt;
  &lt;g class="class d, class b, class e"&gt;
  </code></pre>
  
  <p>I wish to select the 1st and 3rd elements, because they have are both under <code>class b</code>. Any suggestions?
  I thought <code>d3.selectAll(".class b")</code> would work, but it doesn't.</p>