three.js/build/templates/analytics.template

<script>
(function() {
  if (window.location.hostname.indexOf("threejsfundamentals.org") < 0) {
      return;
  }

  function addScript(src, fn) {
    const script = document.createElement('script');
    const firstScript = document.getElementsByTagName('script')[0];
    script.async = true;
    script.defer = true;
    if (fn) {
      script.addEventListener('load', fn);
    }
    script.src = src;
    firstScript.parentNode.insertBefore(script, firstScript);
  }

  addScript('//cdn.webglstats.com/stat.js');
  addScript('https://www.googletagmanager.com/gtag/js?id=UA-120733518-1', () => {
    window.dataLayer = window.dataLayer || [];
    function gtag(){dataLayer.push(arguments);}
    gtag('js', new Date());

    gtag('config', 'UA-120733518-1');
  });
}());
</script>