VRDisplay: свойство isConnected

navigator.getVRDisplays().then((displays) => {
  // If a display is available, use it to present the scene
  if (displays.length > 0) {
    vrDisplay = displays[0];

    // Starting the presentation when the button is clicked: It can only be called in response to a user gesture
    btn.addEventListener("click", () => {
      // Only request presentation if the display is still connected.
      if (vrDisplay.isConnected) {
        vrDisplay.requestPresent([{ source: canvas }]).then(() => {
          // start rendering the app, etc.
        });
      } else {
        console.log("Connection to display lost");
      }
    });
  }
});