title: How to sum the digits of each value in an array to create a new array?
body: <ul>
  <li>Starting array: <code>[1555, 1116, 221, 997]</code></li>
  <li>Ending array: <code>[16, 9, 5, 25]</code></li>
  <li>Where each number in the ending array is the sum of the digits of the corresponding number in the starting array.</li>
  <li>How do I get from the starting array to the ending array?</li>
  </ul>