title: How do you easily create empty matrices javascript?
body: <p>In python, you can do this:</p>
  
  <pre><code>[([None] * 9) for x in range(9)]
  </code></pre>
  
  <p>and you'll get this:</p>
  
  <pre><code>[[None, None, None, None, None, None, None, None, None],
   [None, None, None, None, None, None, None, None, None],
   [None, None, None, None, None, None, None, None, None],
   [None, None, None, None, None, None, None, None, None],
   [None, None, None, None, None, None, None, None, None],
   [None, None, None, None, None, None, None, None, None],
   [None, None, None, None, None, None, None, None, None],
   [None, None, None, None, None, None, None, None, None],
   [None, None, None, None, None, None, None, None, None]]
  </code></pre>
  
  <p>How can I do the equivalent in javascript?</p>