React Interview Questions With Answers

React JS is a powerful and flexible JavaScript library that offers a range of benefits to developers. Its component-based architecture, virtual DOM, and one-way data binding make it fast, reusable, and efficient. It is widely used for building dynamic UIs, mobile apps, e-commerce websites, and enterprise applications. We hope this guide has provided you with a comprehensive understanding of React Interview Questions With Answers and its features, advantages, and use cases. If you’re interested in learning more about React JS, there are several online resources and courses available that can help you get started.

1. What is React?

Ans:- React is Javascript Library. The main aim of using React is to build UI as fast as possible. It is used to create a single-page application.

2. Where we can use React Routing?

Ans:- We can use React Routing on the web (React applications), On the server side with Node JS, and with React native.

3. What is the difference between Link and NavLink?

Ans: 

• By using NavLink we can add custom styles and classes.
• In NavLink we can add all the features of the active link
• We cannot style Link.

 

4. What is nested Routes?

Ans:- Nesting of Routes means to make Route inside a route. We can make tabs or pages inside a page. We can also create multiple nested Routes.

5. Why do we use Link instead of Anchor tag in React?

Ans:- With an anchor tag every time page gets refreshed whenever we click on a hyperlink but by using Link the page does not get refreshed.

6. What is the alternative to NPM?

Ans:- Alternative to NPM is yarn.

7. Can we write one component in another component?

Ans:- Yes we can write one component in another component but we can use it in that component only.

8. Can we use React and Angular both in a single project?

Ans:- Yes we can use not only React but also Angular in a single project because React is a Javascript Library and Angular is a framework.

9. Can we use JSX without React?

Ans:- Yes we can use JSX without React.

10. How React is different from Angular?

Ans:- Difference between React and Angular is:

• React is owned by Facebook and Angular is owned by Google.
• React uses Virtual DOM and Angular uses Real DOM.
• React uses Compile Time Debugging and Angular uses Run Time Debugging.
• React uses server-side rendering and Angular uses client-side rendering.
• React uses One-way data binding and Angular uses two-way data binding.

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11. What are props?

Ans:- Props are nothing but properties in React. Props are always sent from parent to child component. These are used to render dynamically generated data.

12. What is state?

Ans:- A state is an internal object of a class component. State determines the rendering and behavior of a component. They are accessed in class using this.state(). State can be updated using setState() method.

13. What is the use of refs in React?

Ans:- Refs are used to access DOM nodes and React elements which are created in the render method.

14. What is Context API in React Js?

Ans:- Context API in React is a way to pass data through the components without using props. The data is sent globally to all child as well as super child components also using Context API.

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15. What are keys in React?

Ans:- Key is a special value that is used while creating a list of elements in React.

16. What are React Hooks?

Ans:- Hooks are the methods in React that allows using of state and other features of a class component in a functional component.

17. What is useState() in React?

Ans:- It is a hook used to define state in a functional component. It defines an initial state and a function to change that state.

18. What is the use of useEffect() hook in React?

Ans:-It is used to perform different calculations such as fetching of data, setting the title of the document, and manipulating the DOM.

19. What are the different ways to style a component in React?

Ans:- There are the following 3 methods used to style React components-

• Using Inline CSS
• Using CSS stylesheets
• Using CSS Modules

20. What are controlled components in React?

Ans:- Controlled component can maintain their state but the data is controlled by the parent component and values are fetched by using the props.

21. What are pure components in React?

Ans:- Pure components are the single entities that are written in React. These are very easy to write and fast also.

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React JS Interview Questions With Answers on Functions()

22. Why High Order Components are used in React?

Ans:- High Order Components are used to manipulate props and state, to reuse the code and Bootstrap abstraction.

23. useEffect() hook in a functional component replaces which life cycle methods of a class component?

Ans:- componentDidMount(), componentDidUpdate(), and  componentWillMount() methods are replaced by useEffect() hook.

24. When to use useContext() hook?

Ans:- useContext() hook is used to pass the data across your project without using props.

25. How we can apply class attributes conditionally?

Ans:- By using the ternary operator we can apply class attributes conditionally.

26. Can we write multiple components in the same file?

Ans:-Yes we can create multiple components in the same file.

27. Can we use let,var, and const instead of state and props?

Ans:- Yes we can we use let,var, and const instead of state and props.

28. Can we pass the HTML component as a prop?

Ans:- Yes we can pass the HTML component as a prop.

29. What are the phases of Life cycle method?

Ans:- Mounting, Updating and Unmounting are the phases of the life cycle method.

30. Can we use more than one useEffect() in the single component?

Ans:- Yes we can use more than one useEffect() in a single component.

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31. When Hooks are introduced to React?

Ans:- Hooks are introduced in the 16.3 version of React.

32. When we can use React Routing?

Ans:- React routing is used to link components on the web, on the server side with Node JS and also used with React Native.

33. Why use a Link instead of an anchor <a> tag?

Ans:- When we use the anchor tag page gets refreshed every time when we click on link but by using Link page does not get refreshed.

34. Which hooks are used for React Routing?

Ans:- useParams, useSearchParams, useLocation, and useNavigate are the hooks used for React Routing.

35. What are Nested Routes?

Ans:- Creating a Route inside a Route is called as nested route. We can create multiple nested routes.

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