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React JS Knowledge Quiz

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Questions and Answers

What is the primary purpose of the `useState` hook in React?

To manage state changes in a component (correct)

To create a new React component

To handle side effects in a component

To optimize the performance of a component

React Hooks can only be used in class components.

False (B)

What is the purpose of the `key` prop in a React component?

To help React keep track of items in a list and improve performance.

The `jsx` syntax is used to write React components in a _______ way.

declarative Signup and view all the answers

Match the following React lifecycle methods with their purpose:

<code>componentDidMount</code> = Called when the component is mounted to the DOM <code>componentWillUnmount</code> = Called when the component is about to be unmounted from the DOM <code>render</code> = Called when the component is rendered to the DOM <code>shouldComponentUpdate</code> = Called when the component's props or state change Signup and view all the answers

What is the main difference between a controlled and uncontrolled component in React?

A controlled component's value is managed by the state, whereas an uncontrolled component's value is managed by the DOM. Signup and view all the answers

How does React's Virtual DOM improve the performance of a React application?

React's Virtual DOM improves performance by only re-rendering the components that have changed, reducing the number of DOM mutations and resulting in faster rendering. Signup and view all the answers

What is the purpose of the `shouldComponentUpdate` lifecycle method in React?

The <code>shouldComponentUpdate</code> method determines whether a component should re-render when its props or state change. Signup and view all the answers

What is the difference between a functional component and a class component in React?

A functional component is a pure function that takes in props and returns JSX, whereas a class component is a class that extends the React Component class and has its own lifecycle methods. Signup and view all the answers

How does React's context API help in sharing data between components?

React's context API helps in sharing data between components by providing a way to share data between components without having to pass props down manually. Signup and view all the answers