Get awesome marketing content related to Hiring & L&D in your inbox each week

Stay up-to-date with the latest marketing, sales, and service tips and news
Top React.js interview questions to assess candidates

Recruitment | 6 Min Read

Top React.js interview questions to assess candidates


Hiring skilled React.js developers has become quite challenging these days. Though the number of JavaScript engineers has steadily risen, not all candidates are well-versed in React.js. This calls for organizations to optimize their hiring strategies with proper candidate screening using assessment tests and conducting structured interviews to help identify skilled candidates who fit the company culture well.




What is React.js?

React.js is an open-source front-end JavaScript library that was launched in 2013. Used for crafting compelling user interfaces for web applications, React.js is used across several industries, and it is the cornerstone of web development today.


Understanding the key benefits of React.js

Easy to use

React.js is easy for developers with a basic understanding of JavaScript. Writing and maintaining code is also easier with React.js than with regular JavaScript.


Reusable components

React.js applications are built using different components, each with logic and controls. So, the same elements can also be reused throughout the app, helping save time and money. It also means that developers can use parts of codes that have been written for other projects, as well as open-source codes for projects.


Quick rendering

React.js has a virtual document object model, or VDOM, to depict code elements. The virtual DOM is an abstract form of the DOM, and it can identify changes made to the components of the code and render dynamically. The VDOM does not re-render the entire interface and only tweaks the parts that have been updated, which makes the process much more convenient and faster.



With fast rendering, React.js ensures that the page loads quickly, which helps it rank higher on search engine result pages. This is a great advantage for organizations as it can help improve their visibility significantly.


Stable code

React.js involves one-way binding or data flow. This ensures that developers have greater control over the application. It also ensures that the parent elements are not affected whenever child elements are edited.




Top skills React.js developers must possess

Deep knowledge of React.js

Hard skills are an essential requirement for any developer job role. Programmers can build complex web applications using React.js, but only if they possess the skills and experience to use React.js properly.


Coding skills in SQLite

Though React.js is used for front-end development and SQLite is a query language for managing relational databases and back-end development, candidates should have the essential abilities to collate and filter results. Candidates should be able to use SQLite to manipulate databases based on different details.


Clean code writing practices

In order to ensure that projects are done the right way on the first try and that the organization does not have to waste a lot of money and time on projects that take way too long, it is crucial to hire developers who write clean codes. Candidates should understand the YAGNI, SOLID, and DRY coding principles and follow them to create easy-to-understand, efficient code.


Attention to detail

The ability to notice patterns and identify even the smallest of mistakes in long strings of code and memorize complex commands are essential skills that a React.js developer must possess. These abilities need attention to detail. Attention to detail is a skill that is often not given due importance, primarily when recruiting for tech-based job roles. Solving small problems is more accessible for individuals who can notice tiny details that seem out of place.


Critical thinking

Critical thinking skills are crucial for solving problems effectively and meeting challenging requirements to improve applications. Developers with essential skills of thinking do not need to rely on guesswork, and they can also avoid making simple mistakes when writing code.


Hiring React.js developers

Organizations need to establish robust recruitment processes to thoroughly assess the skills and competencies of candidates. The process should comprise skills and aptitude assessment tests for screening applicants and structured interview processes, where every React.js interview question has a clear purpose behind it.




Interviewing candidates

Once the applicants have been screened based on their skills and aptitude using relevant online assessment tests, the shortlisted candidates should be invited for React.js interview questions and answers rounds. The information that recruiters gain through the results of the assessment tests can be used to design personalized interview questions for React.js developers, which can help employers gain a holistic understanding of candidates and their likelihood of succeeding in specific job roles.


Nine advanced React.js interview questions

  1. How to create refs in React.js?
  2. How often does useState update and why?
  3. What are the advantages of using React Hooks?
  4. Why do so many organizations use React.js?
  5. What are the different stages of the React.js lifecycle?
  6. How do you bind class methods to class instances?
  7. What will happen when trying to update the state directly?
  8. Can Hooks replace higher-order components?
  9. What are the advantages of using Flux?


Five sample React.js questions and their answers

1. How to create refs in React.js?

To answer this React.js interview question, candidates must understand that refs are often assigned to instance properties when components are being constructed. Candidates should also be able to explain how React.createRef() is used to create refs in React.js.


2. Why do so many organizations use React.js?

This React.js interview question requires candidates to list the advantages of using React.js for organizations. When candidates respond to this question, they may cover several benefits of using React.js, like how the library can be used to build high-quality user interfaces and create custom components.


3. What are the advantages of using Flux?

Flux is a JavaScript architecture that operates on unidirectional data flows. Candidates should know that Flux offers several advantages for projects involving dynamic data, which can be updated effectively using Flux.


4. What are the advantages of using React Hooks?

Candidates should be able to demonstrate their understanding of React Hooks. React Hooks’ advantages are that they enable developers to effectively handle the setup of side effects, share logic among various components, and enhance the readability of the component tree.


5. How often does useState update and why?

useState is used by developers to enhance the performance of their code by creating queues. The changes are not updated immediately. Candidates should know that the changes are not implemented directly to the state object by state and that the updates occur asynchronously.




Eight advanced behavioral interview questions for React.js developers

  1. Which method should be used to handle events in React.js?
  2. When should refs be used?
  3. When are superconductors used with props arguments?
  4. How is validation used on props?
  5. What method can be used to add attributes conditionally to components?
  6. Which methods can be used to check and improve slow rendering in React.js?
  7. When is useMemo() used in React.js?
  8. How can binding be avoided in React.js?


Five sample behavioral React.js interview questions and their answers

1. When should refs be used?

An understanding that React.js refs can be used to access DOM elements is essential for React.js developers. Candidates should explain here that refs can be used to access an element they have created so the value of the child component can be changed.


2. When is useMemo() used in React.js?

To answer this React.js interview question, candidates should explain that useMemo() can be used by developers to cache the value of a variable along with dependency lists. They should also explain that useMemo() can also be used to avoid unnecessary re-renders and can be helpful in cases involving high processing amounts.


3. When are super conductors used with props arguments?

Here, candidates should be able to explain that props are passed to superconductors for accessing and using these .props in the constructor. When a constructor() function is implemented within a Reac.js component, super() is used to call the parent constructor.


4. How can binding be avoided in React.js?

Arrow functions can be used in class properties to avoid binding. Candidates should be able to convey the same through their answers. They can also add how class properties are a relatively new feature, and developers are required to enable transform-class properties to use them.


5. Which method should be used for handling events in React.js?

Candidates should explain that for handling events, they should be named using camelCase and not lowercase and that when JSX is used, a function is passed as the event handler instead of a string.


Twenty-eight advanced technical React.js interview questions

  1. What is a higher-order component?
  2. What is a mounted component?
  3. What is useState()?
  4. What is an event in React.js?
  5. What are class components?
  6. What are components?
  7. Differentiate between functional and class components.
  8. What are state objects?
  9. What are props objects?
  10. Differentiate between state and props objects.
  11. What is MVC architecture?
  12. What are the architectural differences between React.js and Angular?
  13. What are controlled components?
  14. What are uncontrolled components?
  15. What are the differences between controlled and uncontrolled components?
  16. What are React Hooks?
  17. What is the meaning of ‘three dots’ in React.js?
  18. What are package managers?
  19. What is prop drilling?
  20. What is StrictMode?
  21. What is a Shadow DOM?
  22. How do you explain what a virtual DOM is?
  23. Differentiate between Shadow and virtual DOMs.
  24. Explain the React.js lifecycle methods.
  25. What is a pure function?
  26. What is JSX?
  27. What is Flux architecture?
  28. What are bundlers in React.js?




Five sample answers to advanced technical React.js interview questions

1. What are React Hooks?

Hooks were introduced in React 16.8. They enable developers to use state and other React.js features without writing a class. The feature is called Hook, as it allows developers to ‘hook’ into the features of React.js.


2. What are state objects?

state objects are planned JavaScript objects that developers use in React.js to show information about the current properties of components. state objects can be managed in the component, but the entire component will re-render if changed.


3. What are props objects?

props objects are generally ordinary objects, and candidates should be able to explain that these objects abide by strict properties and that components cannot change their objects.


4. What are class components?

Class components refer to a simple class that includes several functions. These components accept props as arguments and return basic React.js elements. Render functions must be created to use class components, which return React.js elements.


5. What are components?

Components refer to reusable pieces of code that can be used to return React.js elements rendered to a page. Components can return strings, numbers, arrays, and even other components.


Eight tips for using advanced React.js interview questions for candidate assessment

1. Use job descriptions to build a list of questions for React.js interviews

A specific outline and description of job roles can guide building a list of coding and interview questions for React.js developers. The job description can help recruiters determine the criteria candidates should meet and the skills and competencies they should possess so they can tailor the React.js coding and interview questions accordingly.


2. Conduct skills assessment processes before the interview rounds

Not only can relevant skills assessment tests help screen candidates based on required skill sets, but they can also help build a list of questions to ask specific candidates. For instance, if a candidate’s assessment results show they lack technical skills related to React.js components, recruiters can include questions about React.js components to better understand their skills.


3. Review the responsibilities that come with the job role in detail

At the beginning of the interview, after introducing themselves, recruiters can explain the job responsibilities that come with the role in detail. This will help candidates match themselves to the responsibilities and enable them to ask any questions about the job role.


4. Ask generic or commonly asked questions in the beginning of the interview

The first few questions should help recruiters understand candidates’ work-related experience. These React.js interview questions and answers can help recruiters understand how interested candidates are in the job role and also offer them a new opportunity to evaluate the potential performance of candidates in the position in question if they are hired.


5. Maintain consistency

Ensuring consistency between every possible React.js interview question is vital throughout the interviews. Ensuring that a majority of the questions being asked are the same for all candidates can help recruiters compare different candidates and ensure fairness in the recruiting process. Follow-up questions can differ for all candidates based on their answers, but the main list of React.js interview questions should remain the same.


6. Ask open-ended interview questions

Open-ended questions allow recruiters to get more information from candidates. Close-ended questions with ‘yes’ and ‘no’ answers should be avoided completely. However, while using close-ended questions in the interview, following up with another question is necessary to elicit more details from candidates.


7. Invert the process towards the end of interviews

Toward the end of the interview, invite the candidate to ask questions. Inverting the interview process can help candidates determine whether they are suitable for the job role in question. Be prepared to answer the questions honestly and ensure you have all the information candidates need before the interview starts.


8. Inform candidates about when they will hear back

It is a good practice to thank candidates for their time and tell them when to contact them about the interview results. Such practices showcase courtesy and help enhance the overall candidate experience.




Hire top talent with list of advanced React.js interview questions

This list of React.js interview questions and answers can help streamline recruitment processes and make it easy for recruiters to identify and hire top React.js developers. Use these questions as a guide, picking relevant interview questions to build a list for evaluating candidates based on the specific hiring requirements of the organization. Do not forget to integrate skills assessment tests into the interview process to screen suitable candidates from the pool of applicants.


How Mercer | Mettl can help

Mercer | Mettl offers a range of recruitment solutions that enable thorough skills assessment and structured interview processes. The React.js test by Mercer | Mettl is a comprehensive skills assessment that can help recruiters make informed decisions based on candidates’ competencies and job readiness. The assessment not only evaluates cursory domain knowledge but also dives deep into the most critical aspects of React.js development to screen suitable candidates. Apart from this, Mercer | Mettl also offers a wide range of aptitude and cognitive abilities assessments and coding simulators that can help recruiters ascertain if a candidate is a good fit for the job role and the company. Even after optimizing and perfecting the recruitment strategy for hiring React.js developers, don’t forget that recruitment is a process that can always be re-evaluated and improved.





1. How to interview a React.js developer?

2. What are the three important qualities that React.js developers need?

3. What is the highest salary of a React.js developer?

Originally published April 14 2024, Updated April 14 2024

Written by

Harsh Vardhan Sharma, with 6 years of content writing expertise across diverse B2B and B2C verticals, excels in crafting impactful content for broad audiences. Beyond work, he finds joy in reading, traveling, and watching movies.

About This Topic

Hiring a coder requires HRs to go beyond conventional hiring practices and assess the candidate on both knowledge and hands-on skills. A holistic suite of assessments and simulators, used in conjunction, can simplify the technical hiring process and better evaluate programmers and developers.

Related posts

Would you like to comment?


Thanks for submitting the comment. We’ll post the comment once its verified.

Get awesome marketing content related to Hiring & L&D in your inbox each week

Stay up-to-date with the latest marketing, sales, and service tips and news