Quiz for Class Components

Q1: What keyword is used to create a class component in React?

A. function B. class C. component D. extends

Q2: What must a class component extend to become a React component?

A. React.Component B. ReactElement C. React.DOM D. Component

Q3: Which method is mandatory in a React class component?

A. componentDidMount B. constructor C. render D. componentWillMount

Q4: How do you pass props in a class component?

A. this.props B. props C. useProps() D. getProps()

Q5: Where should state be initialized in a class component?

A. render() B. componentDidMount() C. constructor() D. useState()

Q6: What is the correct syntax to define state in constructor?

A. this.state = {}; B. state = {}; C. defineState = {}; D. setState = {};

Q7: Which method is used to update the state?

A. setState() B. updateState() C. changeState() D. modifyState()

Q8: Which lifecycle method is called after a component is rendered?

A. componentDidMount() B. render() C. componentWillMount() D. shouldComponentUpdate()

Q9: Which lifecycle method is called before unmounting?

A. componentDidUpdate() B. componentWillUnmount() C. render() D. componentUnmount()

Q10: How do you bind "this" in a class component?

A. this.bind() B. bind(this) C. this.method.bind(this) D. useBind(this)

Q11: Which method determines if a component should re-render?

A. componentDidUpdate() B. componentWillReceiveProps() C. shouldComponentUpdate() D. componentRender()

Q12: What is returned by the render() method?

A. A string B. An HTML element C. A JSX element D. A function

Q13: What is the default behavior of setState()?

A. Replaces state B. Merges state C. Deletes state D. Resets state

Q14: How can state be passed from parent to child?

A. this.state B. props C. children D. context

Q15: Which method is used to perform side-effects in class components?

A. render() B. constructor() C. componentDidMount() D. shouldComponentUpdate()

Q16: Which keyword is used to inherit in a class component?

A. use B. inherits C. extends D. binds

Q17: What will happen if render() returns undefined?

A. Error B. Nothing displays C. Null is rendered D. Component will crash

Q18: How many render methods can a class component have?

A. Multiple B. One C. None D. Unlimited

Q19: What is the purpose of constructor in class components?

A. Initialize methods B. Initialize state and bind methods C. Render JSX D. Load components

Q20: Which keyword is used to call the parent class constructor?

A. this() B. super() C. base() D. parent()