Sort Multidimensional array in descending order
<p>I have an array that is currently sorted by the first value:</p>

<pre><code>[ [ 'a', 3 ],
  [ 'c', 3 ],
  [ 'd', 1 ],
  [ 'e', 2 ],
  [ 'f', 1 ],
  [ 'g', 1 ],
  [ 'i', 7 ],
  [ 'l', 3 ],
  [ 'o', 2 ],
  [ 'p', 2 ],
  [ 'r', 2 ],
  [ 's', 3 ],
  [ 't', 1 ],
  [ 'u', 2 ],
  [ 'x', 1 ] ]
</code></pre>

<p>I would like to sort the digits in descending order to get: </p>

<pre><code>[ [ 'i', 7 ],
  [ 'a', 3 ],
  [ 'c', 3 ],
  [ 'l', 3 ],
  [ 's', 3 ],
  [ 'e', 2 ],
  [ 'o', 2 ] ......]
</code></pre>