window.addEventListener("gamepadconnected", (e) => {
  console.log(
    "Gamepad connected at index %d: %s. %d buttons, %d axes.",
    e.gamepad.index,
    e.gamepad.id,
    e.gamepad.buttons.length,
    e.gamepad.axes.length,
  );
});

window.addEventListener('deviceorientation', handleOrientation);

function handleOrientation(event) {
  const alpha = event.alpha;
  const beta = event.beta;
  const gamma = event.gamma;
  // Do stuff...
}

navigator.getBattery()
    .then(function(batteryManager) {

        // Get current charge in percentages.
        var level = batteryManager.level * 100;

    })
    .catch(function(e) {
        console.error(e);
    });