React JS MCQs 2

What is the purpose of keys in React lists?

• a) To uniquely identify list items and help React identify which items have changed, added, or removed (Correct Answer)
• b) To apply styling to list items
• c) To determine the order of list items
• d) Keys are not used in React lists

Which method is used to conditionally render components in React?

• a) renderIf()
• b) renderConditionally()
• c) render() method with if-else statements
• d) render() method with conditional rendering syntax like ternary operators or logical && (Correct Answer)

What is the purpose of PropTypes in React?

• a) To define types for React components
• b) To specify default values for props
• c) To validate the props passed to a component (Correct Answer)
• d) PropTypes are not used in React

Which of the following is used to manage state across multiple components in React?

• a) Redux (Correct Answer)
• b) useState hook
• c) Context API
• d) Props drilling

In React, what is the recommended way to perform side effects such as data fetching or DOM manipulation?

• a) Inside the constructor of the component
• b) Inside the render method
• c) Using lifecycle methods like componentDidMount() or useEffect() hook (Correct Answer)
• d) Using setTimeout()

Which of the following is true about PureComponent in React?

• a) It is deprecated in favor of functional components
• b) It automatically implements shouldComponentUpdate() with a shallow prop and state comparison (Correct Answer)
• c) It is used for defining stateful components
• d) It is used for server-side rendering in React

What is the purpose of the ref attribute in React?

• a) To reference an external JavaScript file
• b) To create a reference to a DOM element or a React component instance (Correct Answer)
• c) To define the relative path of a component
• d) To specify the location of a resource

Which method is called after the component is updated and the DOM has been re-rendered in React?

• a) componentDidUpdate() (Correct Answer)
• b) componentWillUpdate()
• c) componentWillMount()
• d) componentDidRender()

What is the purpose of React Fragments?

• a) To create virtual DOM elements
• b) To improve performance by reducing unnecessary re-renders
• c) To group multiple children without adding extra nodes to the DOM (Correct Answer)
• d) To apply animations to React components

Which of the following is NOT a hook provided by React?

• a) useState()
• b) useEffect()
• c) useContext()
• d) createClass()