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React Native · Question Set
State Management & Data Flow interview questions for placements and exams.
Questions
14
Included in this set
Subject
React Native
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Difficulty
Mixed
Level of this set
Go through each question and its explanation. Use this set as a focused practice pack for React Native.
useState allows a functional component to hold local state. It returns an array containing the current state value and a function to update it. Updating the state automatically re-renders the component.
const [count, setCount] = useState(0);
For complete preparation, combine this set with full subject-wise practice for React Native. You can also explore other subjects and sets from the links below.
useEffect runs after the component renders and is used for effects like fetching data, setting timers, or subscribing to events. You can also return a cleanup function to remove listeners when the component unmounts.
useEffect(() => { fetchData(); return () => cleanup(); }, []);useRef stores a value that persists across renders without causing re-renders when it changes. It’s often used to reference DOM or native elements, or to store mutable variables like timers.
const timer = useRef(null);
useReducer provides a predictable way to manage state transitions by dispatching actions. It’s ideal when you have multiple related state values or complex update rules, similar to Redux’s reducer pattern.
const [state, dispatch] = useReducer(reducer, initialState);
Redux provides a single centralized store that holds all application state. It ensures consistent behavior and makes debugging easier with tools like Redux DevTools.
The Redux flow starts when a user interacts with the view, which dispatches an action. The reducer processes the action, updates the store, and the updated state re-renders the view.
The Context API is simple and built into React. It works well for small-scale global data like themes or user preferences. Redux, on the other hand, provides structured state management with reducers, middleware, and debugging tools, making it better for large, complex apps with frequent updates.
Middleware acts as a layer between dispatching an action and reaching the reducer. It is used for logging, asynchronous operations (like Redux Thunk or Saga), and side-effects such as API calls. This keeps reducers pure and predictable.
Redux Thunk is a middleware that allows you to write action creators that return a function instead of an action object. This function can perform asynchronous tasks such as fetching data before dispatching the actual action, making it ideal for network calls in React Native apps.
export const fetchUsers = () => async dispatch => { const res = await api.get('/users'); dispatch({ type: 'SET_USERS', payload: res.data }); };Common issues include unnecessary re-renders, overuse of Context, and not memoizing expensive computations. Use React.memo, useCallback, and useMemo to prevent re-renders, and split contexts when data updates frequently.
You can use AsyncStorage along with redux-persist to save and rehydrate state. This ensures that user data, preferences, or login sessions are retained even when the app restarts.
The store in Redux is a single object that holds the global state tree. Components subscribe to relevant parts of the store and dispatch actions to update it through reducers.
The Context API allows data to be shared globally without manually passing props through multiple component levels. It’s commonly used for global themes, authentication data, or language settings.
Actions are plain JavaScript objects with a type property that describes the event or intent. Reducers use these actions to decide how to update the store’s state.
dispatch({ type: 'INCREMENT' });