Learn React Js MCQs
Prepare React Js MCQs (Multiple choice Questions) for exam and job interviews.
What is the purpose of the `componentDidMount` lifecycle method?
1) To manage state updates
2) To perform actions after the component has been rendered
3) To handle side effects
4) To render JSX
Answer : Option 2
How do you create a context in React?
1) Using `React.createContext`
2) Using `useState`
3) Using `useReducer`
4) Using `React.Fragment`
Answer : Option 1
What does the `useRef` hook return?
1) A state and setState function
2) An array of dependencies
3) A context object
4) A ref object with a `current` property
Answer : Option 4
How do you optimize a React component for performance?
1) Using `React.memo`
2) Using `props` directly
3) Using inline styles
4) Using `setState` in `componentDidMount`
Answer : Option 1
What is the purpose of the `useCallback` hook?
1) To manage side effects
2) To memoize callback functions and prevent unnecessary re-renders
3) To handle state updates
4) To create a new context
Answer : Option 2
What is the purpose of the `useReducer` hook?
1) To manage more complex state logic
2) To create refs
3) To fetch data from an API
4) To handle side effects
Answer : Option 1
How do you create a functional component in React?
1) By extending `React.Component`
2) By using the `useState` hook
3) By using the `useEffect` hook
4) By creating a function that returns JSX
Answer : Option 4
What does the `useState` hook do?
1) Creates a new context
2) Manages state in functional components
3) Creates a ref
4) Handles side effects
Answer : Option 2
How do you pass props to a component?
1) By adding attributes to the JSX tag
2) By using `this.props`
3) By using `setState`
4) By using `useEffect`
Answer : Option 1
What is the purpose of the `useEffect` hook?
1) To manage component state
2) To render JSX
3) To handle side effects in functional components
4) To create refs
Answer : Option 3