GTM Popup.html

  <style>
    #gtm-popup {
      width: 70vw;
      height: 70vh;
      position: fixed;
      background-color: gray;
      color: white;
  
      /* Align content to the middle. */
      display: none; /* hide by default */
      flex-direction: column;
      align-items: center;
      justify-content: center;
      
      /* Sticking modal to the middle */
      top: 50%;
      left: 50%;
      transform: translate(-50%, -50%);
    }
    #gtm-popup-btn {
      display: block;
      border: 1px solid #ccc;
      padding: 20px;
      background-color: orange;
      color: white;
      font-size: 20px;
    }
    .gtm-show { display: flex !important; }
  </style>
  <div id="gtm-popup" class="">
    <h3>Hello world</h3>
    <p>Content here...</p>
    <button id="gtm-popup-btn">Covid Updates</button>
  </div>
  <script src="https://cdn.jsdelivr.net/npm/js-cookie@rc/dist/js.cookie.min.js"></script>
  <script>
    (function() {
      document.querySelector('#gtm-popup-btn').addEventListener('click', function() {
        Cookies.set('gtmPopup', '1', { expires: 99999 });
        document.querySelector('#gtm-popup').classList.remove('gtm-show');
      });
      /* already closed */
      if (!Cookies.get('gtmPopup')) {
        document.querySelector('#gtm-popup').classList.add('gtm-show');
      }
    })();
  </script>