Learn React Js MCQs
Prepare React Js MCQs (Multiple choice Questions) for exam and job interviews.
How do you create a ref in a class component?
1) Using `this.state`
2) Using `React.createRef`
3) Using `useRef`
4) Using `React.forwardRef`
Answer : Option 2
What is the purpose of the `useMemo` hook?
1) To manage state
2) Creates a ref
3) To memoize a value to prevent unnecessary recalculations
4) To handle side effects
Answer : Option 3
How do you use the `useEffect` hook to run only once?
1) By not passing any dependencies
2) By passing an empty array as the second argument
3) By using `useMemo` instead
4) By passing `null` as the second argument
Answer : Option 2
What does `React.Fragment` do?
1) Handles routing
2) Creates a new context
3) Allows grouping of multiple elements without adding extra nodes to the DOM
4) Manages state
Answer : Option 3
How do you update a component’s state in a class component?
1) Using `this.props`
2) Using `this.setState`
3) Using `this.state`
4) Using `this.context`
Answer : Option 2
What is the purpose of the `prop-types` package in React?
1) To manage state
2) To validate the props passed to a component
3) To handle side effects
4) To optimize performance
Answer : Option 2
How do you conditionally render components in React?
1) Using the `useEffect` hook
2) Using `this.state`
3) Using ternary operators or `if-else` statements
4) Using `this.props`
Answer : Option 3
How do you handle errors in React components?
1) Using try-catch in `render`
2) Using `useState`
3) Using Error Boundaries
4) Using `useEffect`
Answer : Option 3
What is the purpose of `React.memo`?
1) To handle side effects
2) To create refs
3) To optimize performance by memoizing components
4) To manage state
Answer : Option 3
How do you handle routing in a React application?
1) Using `react-router` library
2) Using `useEffect` hook
3) Using `useState` hook
4) Using `componentDidMount`
Answer : Option 1