React Interview Questions and Answers

React is a popular JavaScript library used for building user interfaces. It has become increasingly popular over the years and is now widely used in web development. If you're preparing for a React interview, it's essential to have a good understanding of the library's fundamentals. In this article, we'll cover some common React interview questions and their answers.

Table of Contents

1. What is React?
2. What is JSX?
3. What are components in React?
4. What is state in React?
5. What is the difference between props and state?
6. What is the purpose of setState() method in React?
7. What are lifecycle methods in React?
8. What is the difference between controlled and uncontrolled components in React?
9. What is the virtual DOM in React?
10. What are higher-order components in React?

1. What is React?

React is a JavaScript library used for building user interfaces. It was developed by Facebook and is now widely used in web development. React allows developers to build complex user interfaces by breaking them down into smaller components.

2. What is JSX?

JSX is a syntax extension for JavaScript. It allows developers to write HTML-like syntax in JavaScript. JSX makes it easier to write and understand the structure of React components.

3. What are components in React?

Components are the building blocks of React applications. They are reusable pieces of code that can be combined to create complex user interfaces. Components can be either functional or class-based.

4. What is state in React?

State is an object that holds the data that determines a component's behavior and rendered output. It can be changed by the component and its children, but it is not accessible from outside the component.

5. What is the difference between props and state?

Props and state are both used to pass data between components in React. The main difference is that props are passed down from the parent component, whereas state is managed within the component itself.

6. What is the purpose of setState() method in React?

The setState() method is used to update a component's state. When setState() is called, React will re-render the component with the updated state.

7. What are lifecycle methods in React?

Lifecycle methods are methods that are called at specific points in a component's lifecycle. They allow developers to execute code at specific times, such as when a component is mounted or updated.

8. What is the difference between controlled and uncontrolled components in React?

Controlled components are components that have their state controlled by React. Uncontrolled components are components that manage their state internally.

9. What is the virtual DOM in React?

The virtual DOM is a concept in React that allows for efficient updating of the UI. React creates a virtual representation of the DOM and compares it to the actual DOM to determine what needs to be updated.

10. What are higher-order components in React?

Higher-order components (HOCs) are components that take in another component and return a new component. HOCs are used to add functionality to existing components without modifying the original component.

Conclusion

In conclusion, React is a powerful library used for building user interfaces. Understanding its fundamentals is essential for success in a React interview. By studying these common React interview questions and their answers, you'll be better prepared to demonstrate your knowledge and skills to potential employers.

In the future, we can expect to see continued growth and development in the React ecosystem, with new features and functionality being added to the library. Staying up-to-date with the latest trends and best practices in React development will be critical for continued success in this field.