gistfile1.html

<link rel="preload" href="http://myface.com/socializor.js" type="application/javascript" class="socializor-preload">
<script>
  document.ready(function() {
    document.querySelector('.social-button').addEventListener('click', function(event) {
      document.querySelector('.socializor-preload').loaded().then(function(link) {
        var script = document.createElement('script');
        script.src = link.href;
        document.head.appendChild(script);
      });
      event.preventDefault();
    });
  });
</script>