Most Popular React JS Interview Questions & Answers For 2024

Intro

Clearing a React JS interview is not as easy as you may think. Why? Because in order to crack the interview you must have in-depth knowledge of the front-end library. However, if you master the most frequently asked interview questions then you can easily crack the interview. Keeping this in mind, today we are sharing with you some of the most popular ReactJS interview QAs for 2024.

What Is React?

Basically, it is one of the top front-end development libraries that you can use for modern web development. Using it you can easily develop interactive user interfaces. Moreover, it allows you to develop web apps quickly/efficiently by writing less code. Furthermore, all the app components you develop using it are also reusable. In other words, it is a fabulous front-end library and provides tons of benefits to its users. To learn how to develop reusable components using the front-end library in detail feel free to join our React Course For Beginners.

React JS Interview Questions & Answers for 2024

Clearing an interview for the position of React expert is not that easy and requires lots of hard work. However, with the correct plan and mastering React Js Important Concepts and interview questions, you can easily ace your interview. Following are some of the most frequently asked React JS interview questions:

React JS Important Concepts

Below are the top 5 important concepts you should know in React JS.

• Use Higher-order Components (HOCs) - This is an advanced technique useful in React JS that facilitates supercharging and reusing components.
   
• Properly Understanding the useEffect () Hook - This component acts like a middleware that runs after the component has been rendered initially.
   
• Lazy loading images in React - The lazy loading feature allows users to wait until each of the images is about to appear in the viewport before rendering them in the DOM.
   
• Code-splitting in React using dynamic import - React allows the apps to final bundle in one giant file which results in reducing the HTTP Request.
   
• Build Custom Hooks - React JS provides numerous important hooks by default. It also provides the facility to build custom hooks to extend the component logic further.

React JS Fresher Interview Questions

 Here are a few common React JS Fresher Interview Questions with their answers.

1. Why React Is Popular?

Following are some of the key reasons behind the popularity of this robust front-end library:

• Easy to learn
• Simplicity
• High scalability

2. Does React Use HTML?

No, the front-end library does not use HTML. Instead, it uses JSX which is quite identical to HTML. To learn about JSX in more detail feel free to join our React JS Certification Course.

3. What Are the Key Features of ReactJS?

Following are some of the major features of the front-end library:

• Improves SEO
• The library makes it quite easy for developers to develop components. Furthermore, you can also reuse the components that you develop using the Front-end library.
• The code that you write using the library is extremely stable. 
• You can integrate the library with various other frameworks easily.

4. Are There Any Drawbacks to Using React for Development?

Just like every other technology React also has its pros and cons. Following are some of the major drawbacks of using the library for development:

• Developing code with the front-end library can be a little hard. Why? Because it uses JSX/inline template formatting.
• The size of the front-end library is very huge. Thus, it can be overwhelming to master the front-end library.
• You can use the library only to develop the front end of an app.
• It is not a complete framework.
• React users need to have a deep understanding of the MVC framework.

5. What Is Virtual DOM?

Basically, it is the lightweight version or copy of the DOM object. Moreover, it makes it very easy for developers to make changes to the app.

6. Is It Possible to Read a JSX File Using a Browser?

No browsers are not capable of reading JSX files directly. However, they can read JS objects in JSX files. But if you want the browser to read the file entirely you have to transform it into a JS object. For converting the file into a JS object you can take the help of JSX transformers.

7. What is Redux Thunk?

Basically, it is a middleware that you can use to write action creators. Moreover, these action creators return functions in place of actions. Apart from this, you can also use Redux Thunk as a delay function.

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React JS Advanced Interview Questions

Here are common React JS Advanced Interview Questions with their answers.

8. What Is Redux?

Mainly it is a library that you can use for front-end development. Moreover, you can easily run & test apps that are built using the library in different environments. 

9. What Is Flux?

Basically, it is an application architecture that you can use for creating data layers in JS apps. Moreover, the application architecture supports/follows the concept of a unidirectional data flow model. Mainly developers use this application architecture when the app contains dynamic data. To learn how to use the Flux architecture in detail feel free to join our React Online training program.

10. What Are the Key Differences Between a DOM and a Virtual DOM?

Following are the major differences between a DOM and a virtual DOM:

• You can update virtual DOMs quickly. On the other hand, updating real DOM can take a lot of time.
• You cannot update HTML directly with the help of a Virtual DOM. On the other hand, real DOMs can be used for updating HTML.
• Virtual DOM consumes less memory. On the other hand, real DOM consumes lots of memory.

11. What Is the Difference Between MVC and Flux?

Following are some of the major differences between MVC and Flux:

• MVC is an obsolete application architecture. On the other hand, Flux is a new application architecture that you can use for developing data layers in apps.
• MVC architecture can’t work efficiently when the size of the app grows. On the other hand, Flux can work efficiently irrespective of the size of the app.

12. How to Optimize the Performance of a React App?

Following are the things that you can do to improve the performance of a ReactJS app:

• Use PureComponent or React.memo
• Use code-splitting technique
• Optimize component rendering. For this, you can use virtualization libraries like react-window.

You may also read: React Advantages Over Angular

React Js Developer Interview Questions

 Here are common React Js Developer Interview Questions with their answers.

13. How to Handle Form Using ReactJS?

You can handle forms with the front-end library using controlled components, event handlers, and state updates.

14. How Can You Handle Errors With React?

You can use Error Boundaries for handling errors with React.

15. What Are HOCs?

Basically, HOCs are a pattern that enables developers to reuse component logic. Moreover, you can also use higher-order components for data-fetching and state management. The main of higher-order components is to make code reusable and easy to maintain/manage.

16. What Is JSX?

Basically, it is an extension of JS. Using this extension you can write HTML-like code inside a JS code. Moreover, by using JSX you can easily develop efficient and user-friendly apps with React.

17. What Challenges You Can Face With React?

Following are the challenges you can face by using ReactJS:

• You may struggle to manage a complex state.
• Managing dependencies can be quite difficult with React.
• Debugging apps that are built using React can be quite difficult.
• You may face performance issues with large and complex react apps.

18. What Are the Key/Major Differences Between React and Angular?

The following are the main differences between React JS and Angular JS:

• You can use Angular JS for building dynamic web apps. On the other hand, you can use React to build the UI of apps.
• Angular JS framework is built using the TypeScript framework. On the other hand, the React library is built with the help of JS.
• You can use Angular to build robust single-page applications. But you can’t use React for developing single-page applications.

Related Post: React Full Stack Developer Skills

React JS Technical Interview Questions

React JS interview consists of 80% technical interview questions which will help the interviewer understand your capabilities. So it's necessary to have a look at these React JS technical interview questions before going for any interview.

19. Why is there a need for using keys in Lists?

To determine whether items in the lists have changed, been updated, or removed, a key is a unique identifier. It determines which components require a new render instead of rendering them all over is also helpful. 

20. What are forms in React?

Forms are used by React to facilitate user interaction with web applications. Users can interact with the program and enter the necessary data whenever needed by using forms. 

21. What is an arrow function and how is it used in React?

One quick approach to write a function in React is to use an arrow function. When utilizing an arrow function, "this" does not need to be bound inside the constructor. By doing this, issues brought on by React callbacks using "this" are avoided.

22. What are the components in React?

Any React application starts with components, and an application often comprises several components. In essence, a component is a section of the user interface. It divides the user interface into separate, reusable components that may be handled independently.

23. What is the use of render() in React?

Every component needs to have a render () function. The HTML that should be displayed in the component is returned by this function.

24. What is a state in React?

A built-in React object called the state is used to hold data or details about the component. A component's state is subject to change over time. 

25. What are props in React?

Properties are shortened to props. It is a built-in React object that functions similarly to HTML attributes and stores the value of a tag's attributes.

React JS Coding Interview Questions

Here are some of the React JS Coding Interview Questions  Answers are given below.

26. Give an example of functional components

import React from 'react';

function Greeting(props) {

  return <h1>Hello, {props.name}!</h1>;

}

27. Give an example of class components

Example of a class component:

import React, { Component } from 'react';

class Greeting extends Component {

  render() {

    return <h1>Hello, {this.props.name}!</h1>;

  }

}

export default Greeting;

28. How to pass and use the props in React?

import React from 'react';

import ChildComponent from './ChildComponent';

function ParentComponent() {

  const message = 'Hello from ParentComponent';

  return <ChildComponent text={message} />;

}

export default ParentComponent;

29. Give an example of how to manage the state in class components.

import React, { Component } from 'react';

class Counter extends Component {

  constructor(props) {

    super(props);

    this.state = {

      count: 0,

    };

  }

  incrementCounter = () => {

    this.setState({ count: this.state.count + 1 });

  };

  render() {

    return (

      <div>

        <h1>Count: {this.state.count}</h1>

        <button onClick={this.incrementCounter}>Increment</button>

      </div>

    );

  }

}

export default Counter;

export default Greeting;

30. What is the context API?

This feature allows you to share data between components without passing it through props. It helps you pass data through multiple levels of a component tree. The React.createContext function is useful for creating the context API. 

const MyContext = React.createContext();

Conclusion

These are some of the top React JS interview questions that you might encounter while giving your interview. So, make sure you master these interview questions if you want to enhance your chances of cracking your interview. If you do this then you can easily crack your React JS interview without any difficulty. In other words, you will not regret mastering these React Js interview questions.