import { animate, utils, stagger } from 'animejs';

const [ $restartButton ] = utils.$('.restart');

const animation = animate('.square', {
  x: '17rem',
  direction: 'alternate',
  ease: 'inOutSine',
  loop: true,
  delay: stagger(100)
});

const restartAnimation = () => animation.restart();

$restartButton.addEventListener('click', restartAnimation);

<div class="medium row">
  <div class="square"></div>
</div>
<div class="medium row">
  <div class="square"></div>
</div>
<div class="medium row">
  <fieldset class="controls">
    <button class="button restart">Restart</button>
  </fieldset>
</div>