Learn React Js MCQs
Prepare React Js MCQs (Multiple choice Questions) for exam and job interviews.
What is the purpose of `useMemo` hook?
1) To fetch data
2) To manage component state
3) To memoize expensive calculations and avoid unnecessary re-renders
4) To create refs
Answer : Option 3
How do you import a component in React?
1) Using `import` statement
2) Using `require` statement
3) Using `module.exports`
4) Using `include` statement
Answer : Option 1
What is the purpose of React.StrictMode?
1) To enable concurrent mode
2) To check for potential problems in the application
3) To improve performance
4) To handle side effects
Answer : Option 2
How do you conditionally apply CSS classes in React?
1) Using className prop with ternary operators or logical &&
2) Using style prop
3) Using class attribute
4) Using React.Fragment
Answer : Option 1
What is the purpose of useLayoutEffect hook?
1) To perform side effects after layout updates
2) To manage component state
3) To handle events
4) To fetch data
Answer : Option 1
How do you render a list of items in React?
1) Using Array.map method and returning JSX
2) Using Array.forEach method
3) Using Array.reduce method
4) Using Array.filter method
Answer : Option 1
What does useRef hook return?
1) A ref object with a current property
2) A function
3) A state variable
4) A DOM element
Answer : Option 1
How do you handle asynchronous operations in React?
1) Using useEffect hook with async functions
2) Using useState hook
3) Using useRef hook
4) Using useCallback hook
Answer : Option 1
What is the purpose of componentDidUpdate lifecycle method?
1) To perform actions after the component updates
2) To fetch data
3) To handle events
4) To set initial state
Answer : Option 1
How do you prevent a component from re-rendering in React?
1) Using shouldComponentUpdate lifecycle method or React.memo
2) Using componentDidMount lifecycle method
3) Using useEffect hook
4) Using useRef hook
Answer : Option 1