function hasGetUserMedia() {
  return !!(navigator.mediaDevices && navigator.mediaDevices.getUserMedia);
}

function getDeviceAccess() {
  const constraints = {
    video: true,
    audio: true
  };

  const video = document.querySelector("video");

  // todo avoid to play sound (only display video feedback)
  navigator.mediaDevices.getUserMedia(constraints).then((stream) => {
    video.srcObject = stream;
  });
}

if (hasGetUserMedia()) {
  getDeviceAccess()
} else {
  alert("getUserMedia() is not supported by your browser");
}