_layouts/default.html

<!doctype html>
<html>
  {% include head.html %}
  {{ content }}
  <script src="//cdnjs.cloudflare.com/ajax/libs/modernizr/2.8.3/modernizr.min.js"></script>
  <script src="//cdnjs.cloudflare.com/ajax/libs/anchor-js/3.2.2/anchor.min.js"></script>
  <script>
    anchors.options = {
      placement: 'left',
      icon: '#'
    };
    anchors.add();
  </script>
  <!-- Global site tag (gtag.js) - Google Analytics -->
  <script async src="https://www.googletagmanager.com/gtag/js?id=UA-102564547-3"></script>
  <script>
    window.dataLayer = window.dataLayer || [];
    function gtag(){dataLayer.push(arguments);}
    gtag('js', new Date());

    gtag('config', 'UA-102564547-3');

    window.onload = function () {
      function copyToClipboard() {
        const textId = this.id.replace('btn','code')
        const copyText = document.getElementById(textId);
        const text = copyText.textContent || copyText.innerText;

        const input = document.createElement('textarea');
        input.innerHTML = text.replace(/\n$/, '');
        document.body.appendChild(input);
        input.select();
        input.setSelectionRange(0, 99999);
        document.execCommand('copy');
        document.body.removeChild(input);

        this.innerHTML = '✔️';
        setTimeout(() => {
          this.innerHTML = '📋';
        },2000)
      }
    let codes = document.querySelectorAll('.highlight > pre > code');
    let count = 0;
    codes.forEach((code) => {
      code.setAttribute("id", `code-${count}`);
      const btn = document.createElement('button');
      btn.innerHTML = "📋";
      btn.className = "btn-copy";
      btn.setAttribute("id", `btn-${count}`);
      btn.addEventListener("click",copyToClipboard);
      code.before(btn);
      count++;
    });
   }
  </script>
</html>