script.js

const videoElement = document.getElementById('video');
const button = document.getElementById('button');

// Prompt user to select media stream,
// pass to video element,
// then play
async function selectMediaStream() {
  try {
    const mediaStream = await navigator.mediaDevices.getDisplayMedia();
    videoElement.srcObject = mediaStream;
    videoElement.onloadedmetadata = () => {
      videoElement.play();
    }
  } catch(error) {
    console.log("whoops, error here ", error);
  }
}

button.addEventListener('click', async () => {
  // Disable Button
  button.disabled = true;

  // Start Picture in Picture
  await videoElement.requestPictureInPicture();

  // Reset Button
  button.disabled = false;
});

// On Load
selectMediaStream();