title: count empty values in array
body: <p>Given an array:</p>
  
  <pre><code>var arr = [1,,2,5,6,,4,5,6,,];
  </code></pre>
  
  <p>Count how many <strong>empty</strong> values is has: (length - length after removing the empty values)</p>
  
  <pre><code>var empties = arr.length - arr.filter(function(x){ return true }).length;
  
  // return 3
  </code></pre>
  
  <p>or something like this</p>
  
  <pre><code>arr.empties = arr.length;
  arr.forEach(function(x){ arr.empties--  });
  
  // arr.empties returns 3
  </code></pre>
  
  <p>Is this the best way or am I missing something?</p>