title: d3.js: how to use map function?
body: <p>How can I use <code>d3.map()</code> to get <code>[10, 12]</code> out of the following array?</p>
  
  <pre><code>var mydata = [ 
    { '__data__' : 10 }, 
    {'__data__' : 12 }
  ]; 
  </code></pre>
  
  <p>I have been trying this, but it doesn't work:</p>
  
  <pre><code>var mymap = d3.map(mydata, function(d) { 
    return d.__data__; 
  });
  </code></pre>