To send an event named upvote {{ post_title }} when the element with class upvote-button is clicked:

<script>
  window.onload = function() {
    var button = document.querySelector('.upvote-button');
    if (button) {
      button.addEventListener('click', function(event) {
        cabin.event("kudos");
      });
    }
  };
</script>

(ref)

More @srs bsns (lol)