title: Javascript : How group and sum values from multidimensional array
body: <p>I have an array like this:</p>
  
  <p><a href="https://i.stack.imgur.com/MC5nq.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/MC5nq.png" alt="enter image description here"></a></p>
  
  <p>I would like to group and get the sum of each repetition like this:</p>
  
  <ul>
  <li>AGE270: 9</li>
  <li>AGE203: 5</li>
  <li>AGE208: 9</li>
  <li>...</li>
  <li>AGEXXX: n</li>
  </ul>