Question

An AI wrote this React Native screen that subscribes to a native BLE event emitter and updates a heart-rate display. It runs, but the number updates wildly out of order, sometimes flickers backward, and on Android occasionally throws about updating an unmounted component. What's wrong and how would you fix it?

1function HeartRate() {2  const [bpm, setBpm] = useState(0);3  useEffect(() => {4    const emitter = new NativeEventEmitter(BleModule);5    emitter.addListener('hr', (e) => {6      setTimeout(() => setBpm(e.value), 0);   // "defer to be safe"7    });8  }, []);9  return <Text>{bpm} bpm</Text>;10}