The userState read-only property of the IdleDetector interface returns a string indicating whether the user has interacted with the device since the call to start().

Either "active" or "idle" if IdleDetector.start() has been called, or null otherwise.

In the following example, the change callback prints the status of userState and screenState to the console.

idleDetector.addEventListener("change", () => {
  const userState = idleDetector.userState;
  const screenState = idleDetector.screenState;
  console.log(`Idle change: ${userState}, ${screenState}.`);
});