import { createTimer, utils } from 'animejs';

const [ $reverseButton ] = utils.$('.reverse');
const [ $time ] = utils.$('.time');

const timer = createTimer({
  duration: 2000,
  onUpdate: self => $time.innerHTML = self.iterationCurrentTime,
});

const reverseTimer = () => timer.reverse();

$reverseButton.addEventListener('click', reverseTimer);

<div class="large centered row">
  <div class="half col">
    <pre class="large log row">
      <span class="label">iteration time</span>
      <span class="time value lcd">0</span>
    </pre>
  </div>
</div>
<div class="medium row">
  <fieldset class="controls">
    <button class="button reverse">Reverse</button>
  </fieldset>
</div>