The screenState read-only property of the IdleDetector interface returns a string indicating whether the screen is locked, one of "locked" or "unlocked".

Either "locked" or "unlocked" 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}.`);
});