React Interview Questions in 2024

1. What is React?

• React is a JavaScript library for building user interfaces, developed by Facebook. It allows developers to create reusable UI components and efficiently manage the state of those components.

2. What are the key features of React?

• Virtual DOM: React uses a virtual DOM to improve performance by minimizing DOM manipulation.
• JSX: JSX is a syntax extension for JavaScript that allows developers to write HTML-like code within JavaScript.
• Component-Based Architecture: React follows a component-based architecture, where UIs are composed of reusable and self-contained components.
• One-way Data Binding: React follows a unidirectional data flow, where data flows downwards from parent components to child components.

3. What is JSX?

• JSX stands for JavaScript XML. It is a syntax extension for JavaScript that allows developers to write HTML-like code within JavaScript. JSX makes it easier to write and understand React components.

4. What are React components?

• React components are the building blocks of React applications. They are reusable and self-contained units of UI that can be composed to create complex UIs. Components can be either class components or functional components.

5. What is the difference between class components and functional components in React?

• Class components are ES6 classes that extend the React.Component class. They have access to lifecycle methods and state.
• Functional components are JavaScript functions that accept props as arguments and return JSX. They are simpler and easier to understand than class components. With the introduction of React hooks, functional components can also manage state and have access to lifecycle methods.

6. What are props in React?

• Props (short for properties) are a way of passing data from parent components to child components in React. Props are immutable and are used to customize the behavior and appearance of components.

7. What is state in React?

• State is a built-in feature in React that allows components to manage their internal data. Unlike props, which are passed from parent components, state is managed internally by components and can be updated using the setState() method.

8. What are React lifecycle methods?

• React lifecycle methods are special methods that are automatically invoked at different stages of a component’s lifecycle. Some common lifecycle methods include componentDidMount(), componentDidUpdate(), and componentWillUnmount().

9. What are React hooks?

• React hooks are functions that allow functional components to use state and lifecycle methods. Some commonly used hooks include useState(), useEffect(), and useContext().

10. What is the significance of keys in React lists?

• Keys are special attributes that provide a unique identity to each element in a list. They help React identify which items have changed, been added, or been removed in a list, enabling efficient updates to the UI.

These questions cover some fundamental concepts of React development and are commonly asked in interviews. Depending on the level of the interview and the specific job role, you may encounter more advanced questions related to topics such as React Router, Redux, context API, performance optimization, and testing in React.