10 ReactJS Interview Questions (With Example Answers)

Updated 19 September 2022

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ReactJS is a JavaScript framework that acts as a catalog of reusable components. Computer programmers or web developers use it to create interactive user interfaces. If you appear for an interview for a role that uses ReactJS, you should expect some technical questions. By taking the time to review some of these questions, you can give yourself the best chance of presenting yourself as a qualified candidate during the interview.

In this article, we review some common ReactJS interview questions, along with sample answers to help you craft your own responses and a few tips to help you succeed in your ReactJS interview.

ReactJS Interview Questions With Sample Answers

Here are a few questions the interviewer might ask you during a programming interview about ReactJS, along with sample answers:

1. How would you describe ReactJS to someone with no programming experience?

An interviewer uses this interview question to gauge your understanding of ReactJS and how well you can articulate it outside of your industry. Answering this question well will showcase that you understand the real nuances of the applications of the framework. This question also presents a great opportunity to showcase your quick thinking and communication skills.

To answer this question, use a relatable example that someone with no programming experience can relate to.

Example: "ReactJS is a programming tool created by Facebook. It is used to manage the visual layout of mobile and web formats of a webpage. For example, visual elements include everything you can interact with, such as like buttons or search bars. Another way of looking at ReactJS is by viewing it as a library for all of these visual elements where you can easily search and reuse them."

2. When should you use refs in ReactJS?

The interviewers ask this question to check your in-depth knowledge regarding specific aspects of the ReactJS framework. To answer this question, define refs and explain their situational importance.

Example: "Refs are the tools within a framework that store existing components and create related elements. They are useful when there is a need for an additional method to be added to a component. This is because their storage function helps us take DOM measurements."

3. What is JSX?

Interviewers ask this question to determine your understanding of JSX and its relation to JavaScript programming. To answer this question, define JSX and provide insights into its significance within ReactJS.

Example: "JSX is a type of XML/HTML syntax that helps convert ECMAScript to JavaScript code. It is important because it can help create DOM-like structures that allow it to be placed into the same file as JavaScript, where it can be further converted into JavaScript code."

4. What is Redux and what are its components?

Redux is a library in ReactJS. The interviewers ask this question to determine if you are familiar with this type of library. Your answer should go beyond a basic definition of Redux and explain how it functions within ReactJS. To answer this question, briefly explain what Redux is and where it is used. You can also mention the components of Redux to highlight the depth of your knowledge.

Example: "Redux is a popular library that is utilised for front-end development. It has no dependencies and is often used to help in the creation of JavaScript applications. Redux is made up of three components: actions, reducers and the store."

5. What is the difference between state and props?

As the interview keeps moving forward, the interviewer will start asking you questions about specific elements and functions in ReactJS. This is one such question. To answer this question well, briefly define the two elements and identify the areas in which they differ from each other.

Example: "State can be defined as the fundamental element that determines the functions and characteristics of a component within ReactJS, whereas props or properties, are transferred from a parent component to a PureComponent and are considered to be unchangeable."

6. What is the difference between DOM and virtual DOM?

This question continues the line of questioning about specific elements and functions in ReactJS. This question requires you to recall information about the document object model. To answer this question, briefly explain the difference between the two. You may also touch upon how the two are related.

Example: "DOM is considered an abstraction of an HTML code that provides a visual representation of the written text displayed by the HTML code. Virtual DOM is related to HTML DOM in that it is considered to be derived from it and is therefore considered an abstraction of an abstraction."

7. What are stateless components?

The interviewer asks this question to check your understanding of the basic concepts. Your answer to this question should be beyond a definition of terms. Your answer should explain the function of a stateless component in addition to its definition.

Example: "Stateless components are components that, instead of possessing their own state, take on whatever form that is applied to them. For this reason, they can also be called reusable components."

8. What are some advantages of using ReactJS?

The interviewers ask this question to gauge your understanding of ReactJS and how it positively contributes to web development. When answering this question, draw from your practical knowledge of having used ReactJS instead of simply talking about the theory. Such an approach highlights both your knowledge and your experience with the framework. You may also get a similar question asking for disadvantages instead, so prepare for that as well.

Example: "Some advantages of using ReactJS are that it helps with search engine optimisation and its makeup contributes to easy maintenance and readability. It also helps web developers utilise java coding with little to no difficulty."

9. What is the significance of the render() function?

This question tests the depth of your knowledge. To answer this question well, go beyond a definition and a theoretical answer and explain the render() function's purpose within a larger framework.

Example: "The render() function is significant as it plays an instrumental role in updating the UI. A render() is assigned to every ReactJS component and helps return a single ReactJS element when it is passed to the DOM."

10. How would you compare functional components to class components?

The interviewers ask this question to gauge your understanding of the two different components. Components are important concepts in ReactJS and hence you should not only define these terms but compare their significance within ReactJS. To answer this question well, you should reflect on your practical understanding of the significance of these two types of components.

Example: "A functional component can be considered a stateless component whose function is to return a react element, whereas a class component is a component that allows web developers to access stores and therefore can have a state."

Tips To Prepare For Your ReactJS Interview

Below are some important tips to improve your chances of success in a ReactJS interview:

Research the role and the company

Research the role and the company you are interviewing for to have an accurate idea of the work you will be doing. Study all requirements to ensure you can confidently fill the role. Understanding the role well helps you anticipate the questions that you may be asked in an interview.

Build experience

For roles with specific requirements, you may need to build your experience. Try working on personal projects to develop your coding skills. You may also try building experience with open source projects and volunteer work. You may also consider taking up small freelance gigs related to ReactJS programming. This will help you both build up your CV and earn some money on the side.

Improve your technical knowledge of ReactJS

ReactJS interviews are quite technical in nature. Hence, preparing for your interview will include familiarising yourself extensively with the framework. There are many resources available to help you learn ReactJS. You can find books, online courses and college classes to teach you everything from basics to the most advanced concepts.

Practice mock interviews

If you believe you are proficient with the framework, find some practice interview questions online. Many of these questions will quiz you on your vocabulary, level of fluency and problem-solving skills. You can then practice these questions in a mock interview setting with your friends or family members' help. This will help you prepare mentally on how you would approach such questions in front of the interviewer.