how to format a date in java html script

Question

Hi I've a script like this:

  <script src="https://www.gstatic.com/firebasejs/8.8.1/firebase-app.js"></script>
  <script src="https://www.gstatic.com/firebasejs/8.8.1/firebase-firestore.js"></script>
  
  <script>
    const d = new Date();
    let timestamp = d.toUTCString();

That timestamp gives me a string format like 'Sat, 24 Jun 2023 16:50:25 GMT' I would like to format it like '2023-06-19T10:07:43.109149' instead.

How could I do please?