html

<!-- Simple pop-up dialog box -->
<dialog id="dialog">
  <form method="dialog">
    <button type="submit">Close</button>
  </form>
</dialog>

<p>
  <button id="openDialog">Open Dialog</button>
</p>
<p id="dialogStatus"></p>

<script>
  (() => {
    const openDialog = document.getElementById("openDialog");
    const dialog = document.getElementById("dialog");
    const text = document.getElementById("dialogStatus");

    function openCheck(dialog) {
      if (dialog.open) {
        text.innerText = "Dialog open";
      } else {
        text.innerText = "Dialog closed";
      }
    }

    // Update button opens a modal dialog
    openDialog.addEventListener("click", () => {
      dialog.showModal();
      openCheck(dialog);
    });

    dialog.addEventListener("close", () => {
      openCheck(dialog);
    });
  })();
</script>