React has become one of the most popular tools to build fast and modern web applications. Because of this, many companies ask React questions during job interviews. If you are preparing for a job role in web development, you must know the React basics and advanced topics.
These questions are useful for both beginners and experienced learners. Whether you are looking for react js interview questions or react interview questions for freshers, this article will help you score well.
What is React?
1. What is React?
React is a JavaScript library used to build user interfaces, especially for web apps. It helps make pages fast and easy to change.
2. Who created React?
React was created by Facebook. Later, it became open-source so many developers can use it.
3. What makes React different from other libraries?
React uses something called the Virtual DOM. This makes React faster than many other libraries.
Basics of React
4. What is JSX?
JSX is a special way to write HTML inside JavaScript. It looks like HTML but runs in JavaScript.
5. Why do we use JSX?
We use JSX because it makes writing UI code easier and cleaner.
6. What is a component?
A component is a piece of UI. In React, everything is made of components.
7. What are props?
Props are values we pass from one component to another.
8. What is state?
State stores data inside a component. When state changes, UI updates automatically.
9. Difference between state and props?
State is private and can change inside a component. Props are passed from parents and cannot change inside child.
React Functional and Class Components
10. What is a functional component?
A functional component is a type of component written as a function.
11. What is a class component?
A class component is written using a class and can have state in older React versions.
12. Which one is used more now?
Functional components are used more now because they are simpler and work with hooks.
Hooks – Key Features in React
13. What are hooks?
Hooks are special functions that let you use state and other React features inside functional components.
14. What is useState?
useState allows you to add state in a functional component.
15. What is useEffect?
useEffect helps run code when component loads or when data changes.
16. Why do we use useEffect?
We use useEffect for API calls, timers, or actions when data changes.
Working with Lists and Keys
17. How do you display a list in React?
You use the .map() method to show lists.
18. Why are keys needed in lists?
Keys help React find and update list items fast.
Events and Forms
19. How do you handle events in React?
You use event attributes like onClick, onChange, and functions.
20. How do you handle form input in React?
You bind form input to state and update it using event handlers.
React Routing
21. What is React Router?
React Router lets you change pages in a React app without reloading.
22. Why use React Router?
It gives a smooth user experience by loading only parts of the page.
API and Data Fetching
23. How do you fetch data in React?
You can use fetch or axios inside useEffect to get data from servers.
24. What is axios?
Axios is a tool to make API calls easily.
Conditional Rendering
25. What is conditional rendering?
Showing content based on some condition is conditional rendering.
26. How do you do it?
You can use if, ternary, or logical operators to show or hide content.
React Best Practices
27. Why break UI into components?
Breaking UI makes code reusable and easier to manage.
28. What is lifting state up?
When two components need same data, you move state up to a parent component.
Advanced React Concepts
29. What is context in React?
Context provides data to many components without passing props at every level.
30. Why use React context?
It helps share data like theme or user info across the app.
31. What is lazy loading?
Lazy loading loads code only when needed. This makes app faster.
Optimization and Performance
32. How can you improve React performance?
Use keys, memo, PureComponent, and code splitting for better speed.
33. What is React.memo?
React.memo tells React to skip re-rendering a component if props don’t change.
React Testing and Tools
34. How do you test React?
You can use tools like Jest and React Testing Library.
35. Why test React apps?
Testing finds bugs early and makes code stable.
Deployment and Build
36. How do you build a React app?
You use npm run build to make code ready for production.
37. Where can you deploy React apps?
You can deploy React apps on Netlify, Vercel, GitHub Pages, and cloud servers.
React Interview Tips
38. What should freshers focus on?
Learn basics like components, state, props, and hooks.
39. How to answer React interview questions with confidence?
Practice code, build projects, and read documentation.
40. Why React skills are in demand?
React is fast, easy to learn, and widely used by many companies.
Final Tips for Freshers and Job Seekers
Preparing for react js interview questions can seem hard, but if you start with basics and practice, it becomes easy. Always build small projects to show in interviews. Practice, read real code, and solve problems.
If you want full training, Brillica Services provide full stack web development course. The course covers React from basics to advanced, along with live projects, so you can learn real skills and prepare for jobs.
Conclusion
React is one of the top skills for modern web development. From beginners to experienced developers, everyone must know these react interview questions and answers to succeed in job interviews. Keep learning, keep coding, and use practice projects to grow your confidence.