React.js Quiz

What is React.js?

• A library for building user interfaces

• A backend framework

• A database management system

• A CSS preprocessor

What is the purpose of JSX in React?

• A JavaScript framework

• A syntax extension that allows writing HTML inside JavaScript

• A tool for testing React applications

• A server-side rendering tool

Which method is used to update the state in a React component?

• setState()

• getState()

• changeState()

• updateState()

Which hook is used to manage side effects in functional components?

• useState

• useEffect

• useRef

• useContext

What is the default behavior of the setState() method?

• It updates the state synchronously

• It replaces the entire state

• It merges the new state with the old state

• It does not affect the state

What does 'lifting state up' refer to in React?

• Passing the state down through props

• Moving the state to a common parent component

• Deleting state from a component

• Moving state from a parent component to a child component

What does the key prop help with in lists of elements in React?

• Ensuring each element is unique

• Optimizing rendering performance

• Handling asynchronous updates

• Preventing re-renders

Which of the following is true about React fragments (<>)?

• They are used to group multiple elements without adding an extra node to the DOM

• They provide a way to fetch API data

• They are used to wrap CSS styles

• They represent a way to render elements conditionally

What is the purpose of useRef in React?

• To trigger re-renders

• To create a mutable reference to store values that persist across renders

• To manage component lifecycle methods

• To update the state asynchronously

What does React's componentDidMount lifecycle method do?

• It is called when a component is first rendered

• It is called before a component is unmounted

• It is called every time a component updates

• It is used for conditional rendering