Top 40 Infosys React Interview Questions and Answers

Preparing for the Infosys React interview requires knowledge of React fundamentals, state management, and component lifecycle. This interview aims to assess your React expertise and distinguish yourself as a developer. Your success in the interview will depend on your strong understanding of React principles, including state management, component lifecycle, and JSX components.  Whether you’re a fresher, intermediate, or experienced developer, being prepared with the right questions and answers can make all the difference. In this blog, we have compiled some of the commonly asked Infosys React interview questions tailored to different experience and skill levels, along with tips to help you succeed.

Infosys React Interview Questions for Freshers

Infosys interview questions for ReactJS freshers usually cover fundamental React concepts, JavaScript basics, and basic HTML/CSS. You can anticipate questions about lifecycle methods, JSX, virtual DOM, properties, state, and components. The interview may also cover front-end principles like Redux, React callbacks, and performance optimization. Here are some important Infosys ReactJS interview questions to help you prepare for the fresher screening process.

Q1. What is React, and what advantages does it offer over other front-end frameworks?

Sample Answer: React is a JavaScript library for building user interfaces, mainly focused on the view layer. It’s not a full framework like Angular, which makes it more flexible and easier to integrate into projects. The key advantages are:

• Performance: It uses a virtual DOM for faster updates.
• Reusable Components: Encourages reusability, which makes code easier to maintain and scale.
• Flexibility: You can adopt React gradually without rewriting an entire codebase.

Q2. What is JSX?

Sample Answer: JSX, or JavaScript XML, is a syntax extension for JavaScript commonly used with React. It allows developers to write HTML-like code directly within JavaScript, making it easier to create and manage user interface components in a more readable and intuitive way. 

Q3. What are React Components?

Sample Answer: React components are reusable building blocks for the user interface. They allow you to split the UI into independent, reusable pieces, making development more manageable.

Q4. What are ‘Functional Components’ and ‘Class Components’ in React?

Sample Answer: Functional components are simpler components written as functions that return JSX. On the other hand, class components use ES6 classes and have access to lifecycle methods.  

Q5. What are React Hooks? Can you explain useState and useEffect?

Sample Answer: React Hooks are functions that enable functional components to manage state and lifecycle features. useState is a Hook that enables state variables to be used in functional components. It returns an array containing two elements: the current state value and a function to alter it. On the other hand, useEffect is used to handle side effects, such as fetching data, setting up subscriptions, or manually modifying the DOM. By default, it runs after every render.

Q6. What is state management, and how do you manage ‘state’ in React? 

Sample Answer: In React, state management refers to the process of handling and updating data within an application and its components. For functional components, I utilize the useState hook to manage state, while in class components, I rely on the this.setState method to update the state.

Q7. What is the Virtual DOM, and how does it work? 

Sample Answer: The Virtual DOM (Document Object Model) is a memory-resident, lightweight copy of the actual DOM that enables JavaScript frameworks such as React to efficiently update the user interface. To enhance performance, frameworks can identify minimal changes and implement them efficiently by comparing the Virtual DOM with the real DOM.

Q8. How does React handle events?

Sample Answer: React handles events using a synthetic event system, which is a wrapper around the browser’s native events. This system ensures consistent behavior across different browsers and improves performance by reusing event objects through event pooling (in older versions). React events are also named using camelCase (e.g., onClick instead of onclick) and work similarly to native DOM events but with added cross-browser consistency.

Also Read: Infosys Python Interview Questions

Q9. What is the difference between props and state in React? 

Sample Answer: In React, props and state are both basic JavaScript objects that contain information to affect the output of render. However, they serve distinct purposes. Props are read-only properties that are transferred from a parent component to a child. Whereas a state is a local variable that is administered by a component and can be modified over time.

Q10. What is the purpose of keys in React?

Sample Answer: Keys in React are essential for the efficient identification and tracking of changes in lists of elements. React employs keys as distinct identifiers for each item when rendering a list. This enables React to ascertain which items have been added, removed, or reordered, and to update the DOM accordingly.

Q11. What are the different lifecycle methods in React?

Sample Answer: React’s component lifecycle is a series of methods that manage a component’s life from creation to destruction. Lifecycle methods include componentDidMount, componentDidUpdate, and componentWillUnmount for class components, and useEffect for functional components.

Q12. What is the method of handling page submissions within React?

Sample Answer: Page submissions can be managed in React by employing state to manage form data.  Upon submission of the form, an event handler is called, which typically validates the form data before transmitting it to the server or executing another action.  The event handler alters the state in response to user input and mitigates the default form submission by utilising React’s controlled components to manage the process.

Q13. Which methods can be used to maximize performance outputs in React-based systems?

Sample Answer: Developers for React-based systems can use several methods to minimise unneeded rendering, enhance load times, and maximise resource use to increase system performance. Some important ways to boost performance are listed below:

• Using React’s PureComponent for Class Components: By only updating when the component’s props or state have changed, PureComponent automatically runs the shouldComponentUpdate function to stop needless re-renders.
• For functional components, implement React.memo: A higher-order component called React.memo guarantees that functional components only re-render when their props change. This, hence, lowers the number of renders by memoizing them.
• Lazy loading: This function lets components load only when required, therefore boosting application speed and performance by lowering the initial load time.
• Reduce Unneeded Re-renders Using Class Components: By using shouldComponentUpdate, you can explicitly determine when a component should re-render, therefore lowering needless updates and enhancing general performance.

Q14. What is the purpose of React Router?

Sample Answer: React Router is a library that offers features for routing and navigation in React applications. It allows the development of single-page applications (SPAs) that render various components according to the URL, without necessitating a complete page refresh. User experience can be improved by enabling seamless transitions between various perspectives.

Infosys React Interview Questions for Mid-Level Candidates

For mid-level candidates, Infosys typically asks interview questions that focus on the deep concepts of React, state management, component lifecycle, and performance optimisation. Given below are some Infosys React interview questions for mid-level candidates to test your knowledge and be prepared for the interview:

Q15. What approach do you use for managing extensive state in your React applications?

Sample Answer: A common method for managing extensive state in React is the utilisation of libraries such as Redux or MobX, by using React’s built-in Context API and plugins such as useReducer or useContext. These libraries facilitate CSM, which simplifies the management of intricate data flows.

Q16. What is the purpose of memoization within React?

Sample Answer: The purpose of memoization in React is to enhance performance by caching the results of costly function calls or component renderings and utilising them when the inputs (props or dependencies) remain constant.

Q17. Explain the concept of higher-order components (HOC) in React.

Sample Answer: A Higher-Order Component (HOC) in React is a design pattern used to share common logic across multiple components. It is a function that takes a component as its input and returns a new component with additional behavior or props. HOCs allow developers to abstract and reuse component logic, such as authentication, data fetching, or access control, without repeating code. It is a pattern that is a result of the compositional nature of React, rather than a feature of the React API.

Q18. How do you deal with asynchronous operations within React?

Sample Answer: Asynchronous operations in React are predominantly managed by the useEffect hook, which is frequently used in conjunction with async/await to achieve a cleaner syntax. By employing this methodology, components can engage with external APIs or execute time-consuming activities without impeding the rendering process.

Q19. What is the importance of the ‘key’ in lists in React?

Sample Answer: In React, the key attribute is useful for efficiently updating and rendering lists. It helps React identify which items have changed, been added to, or removed from, allowing the virtual DOM to minimize re-renders and preserve component state where possible. Without unique keys, React cannot reliably track elements, which may lead to performance issues or unexpected behavior when the list changes.

Q20. How do you deal with error boundaries while using React?

Sample Answer: In React, you deal with error boundaries by creating components that catch JavaScript errors in their child component tree during rendering, lifecycle methods, and constructors. To implement an error boundary, you create a class component that defines either or both of the static getDerivedStateFromError() and componentDidCatch() lifecycle methods. This component can then render a fallback UI instead of crashing the entire app. Error boundaries help isolate failures and improve the user experience by preventing full application crashes.

Q21. Which techniques help enhance the speed of React applications?

Sample Answer: To enhance the speed of React applications, I use techniques like memoization to prevent unnecessary re-renders, code-splitting and lazy loading to reduce initial load time, and optimizing state management to avoid prop drilling and redundant updates. I also use performance tools like React DevTools to identify and fix bottlenecks.

Q22. Describe the function of Context API and its use. 

Sample Answer: The Context API in React facilitates the automatic sharing of data, frequently state, or functions, among multiple components within a component tree, eliminating the necessity for laborious prop drilling. This streamlines the process of managing global states and prevents the time-consuming and complex process of passing props through numerous nested components.

Q23. How does React manage elements between controlled and uncontrolled components?

Sample Answer: Form data is managed by React state for controlled components, while unconstrained components are responsible for managing their state. Compared to uncontrolled components, which offer a simpler implementation for fundamental forms, controlled components offer superior control over the data flow.

Q24. What is React’s useRef hook, and how is it used?

Sample Answer: The useRef hook in React is used to persist values across renders without causing re-renders when the value changes. It’s commonly used to reference DOM elements directly or to store mutable values like timers or previous state. You create a ref with useRef(), assign it to an element’s ref attribute, and access the DOM node or value via ref.current.

Q25. What procedures can be used to protect the React application from security threats?

Sample Answer: To protect a React application from security threats, I follow best practices like sanitizing user input to prevent XSS attacks and using HTTPS to secure data transmission. I avoid direct DOM manipulation, implement proper authentication and authorization, manage sensitive data on the backend, and keep dependencies updated to patch known vulnerabilities.

Q26. How do you handle conditional rendering in React?

Sample Answer: Conditional rendering in React allows you to render different UI elements based on certain conditions. JavaScript operators such as if, ternary (? :), or logical && let you decide what to show. For instance, you may display several components depending on the state or props, guaranteeing that the appropriate material is presented to the user depending on their interaction or data retrieved.

Q27. How do you optimize the bundle size in React applications?

Sample Answer: To optimize the bundle size in React applications, I use techniques like code splitting with React.lazy and Suspense to load components only when needed, reducing the initial load time. I also enable tree shaking to eliminate unused code during the build process. Additionally, I use tools like Webpack to further optimize the output by minifying code and analyzing bundle content for unnecessary dependencies.

Q28. Describe your strategy for sibling component communication in React. 

Sample Answer: To manage communication between sibling components in React, I lift the state to their common parent component. This parent then passes the state down to each sibling as props, allowing them to share data and interact with each other. If the communication needs become more complex, I use a state management solution like Redux or React Context to handle global state and facilitate communication across multiple components without prop drilling.

Infosys React Interview Questions for Experienced Candidates

For experienced developers, Infosys interviewers dive deep into scalability, performance, and advanced React patterns. You’ll be expected to discuss why you chose a certain approach in a complex situation. Questions may involve high-level concepts and integration in enterprise-level applications. You may also face system design discussions around front-end architecture and deployment pipelines. Here are some Infosys React interview questions for experienced professionals.

Q29. What methods do you use to enhance performance in extensive React application frameworks?

Sample Answer: To optimise the performance of extensive React applications, I frequently implement strategies such as code splitting, memoization, virtualisation, and efficient data retrieval. These methods contribute to the enhancement of the application’s overall responsiveness, the reduction of re-renders, and the optimisation of loading times.

Q30. What methods do you use to make React application components reusable?

Sample Answer: To develop reusable React components, I employ advanced techniques such as compound components and container components, optimize the use of properties, maintain the focus of components, and leverage React Hooks. In addition to facilitating the reuse of UI building blocks throughout your application, this method also renders the code more modular and simpler to maintain.

Q31. How do you manage state handling across a complex React application development?

Sample Answer: In a complex React application, I manage state by using a combination of local state, Context API, and external state management libraries like Redux or Zustand. For component-specific state, I rely on useState and useReducer. For global state, I use Context API for simpler scenarios or Redux for more complex state logic. I also ensure that the state is lifted appropriately to avoid unnecessary prop drilling and maintain a clear flow of data across components. Additionally, I follow best practices like normalizing data, using selectors, and keeping the state structure flat to improve performance and maintainability.

Q32. Can you explain how to handle API calls in a React application?

Sample Answer: In React, API calls are predominantly managed through the Fetch API or libraries such as Axios. This is typically done within the useEffect hook in functional components or the componentDidMount lifecycle method in class components. The data is retrieved or sent from a server with these operations, and the component’s state is subsequently updated, resulting in re-renders.

Q33. What approach do you use to maintain the communication flow in substantial React application components?

Sample Answer: When communicating between components, I implement a combination of state extraction and context. My objective is to guarantee that components adhere to the single responsibility principle, which facilitates communication without obstructing the codebase.

Q34. What strategy do you use to handle forms in React when dealing with complex forms?

Sample Answer: I utilise React features, particularly useState, to manage state for intricate forms, with a particular emphasis on local form data. On the run, I validate inputs and employ controlled components to guarantee that the form’s data is by the component’s state.

Q35. How do you ensure accessibility (a11y) in your React applications?

Sample Answer: To ensure accessibility (a11y) in React applications, I follow best practices like using semantic HTML elements, adding appropriate ARIA roles and attributes, ensuring proper keyboard navigation, and making sure interactive elements are focusable and have meaningful labels. I also test the app with screen readers and tools like Lighthouse to identify and fix potential accessibility issues. Additionally, I ensure sufficient color contrast and provide text alternatives for images to accommodate users with different needs.

Q36. Which process do you use for implementing routing in React applications?

Sample Answer: In React applications, routing is typically implemented using the react-router-dom library, which offers components such as BrowserRouter, Routes, and Route to facilitate navigation. In general, the procedure entails the installation of the library, the importation of essential components, the definition of routes with their corresponding components, and the packaging of the application with a router.

Q37. How do you debug React applications?

Sample Answer: To debug React applications, I primarily use React Developer Tools to inspect the component tree, check component props and state, and monitor the component lifecycle. I also rely on Chrome Developer Tools for debugging JavaScript, inspecting network requests, and examining the rendered DOM. For deeper insight into state changes and lifecycle methods, I log useful information to the console, such as the current state or props. Additionally, I write unit tests and integration tests using libraries like Jest and React Testing Library to ensure the app’s functionality is correct and to catch potential issues early.

Q38. How do you manage version control and deployment for large React applications?

Sample Answer: To manage version control and deployment for large React applications, I follow a structured approach using Git and GitHub for version control. I adopt feature branching for better collaboration and maintain a clean, organized commit history. For deployments, I set up CI/CD pipelines using tools like GitHub Actions or Jenkins. These pipelines automate testing, linting, and deployment processes, ensuring reliable, error-free deployments. I also use versioning strategies like semantic versioning (semver) to manage releases and ensure compatibility between different versions of the app. Additionally, I keep the codebase modular by organizing components into reusable, well-documented units, making the application scalable and maintainable.

Q39. How do you handle error handling and boundary cases in a React application?

Sample Answer: In React, I handle error handling and boundary cases by implementing Error Boundaries — components that catch JavaScript errors in their child components and display a fallback UI. I also ensure that critical logic has proper error handling using try-catch blocks and validate inputs to prevent unexpected behavior. For asynchronous operations, I use async/await with try-catch to handle errors effectively, and I provide meaningful error messages to improve debugging and user experience. Additionally, I use libraries like Sentry for error tracking in production environments.

Q40. What methods do you use to regulate updates and dependencies in a React application?

Sample Answer: To manage updates and dependencies in a React application, I use package managers like npm or Yarn to handle dependency installations and updates. I regularly check for outdated packages and use tools such as npm-check-updates or yarn outdated to identify dependencies that need updating. For smoother updates, I prefer to follow the semver (semantic versioning) strategy to avoid breaking changes. I also ensure compatibility by reviewing release notes for major updates and running automated tests to verify that updates do not introduce issues.

Tips to Prepare for the Infosys React Interview

To prepare effectively for the Infosys React interview, focus on mastering React fundamentals, sharpening JavaScript skills, understanding state management, improving your problem-solving skills, and reviewing real-world projects to showcase your experience. Here are essential tips to help you ace the interview and land the job:

1. Master the Fundamentals of React: To excel in your Infosys React interview, start by mastering the fundamentals of React. Focus on core concepts like components, JSX, state, props and hooks, state management, etc. Build small projects to apply these concepts in practice.
2. Improve your JavaScript Skills: Since React is built on JavaScript, a strong command of modern JavaScript is essential. Review key ES6+ features such as arrow functions, destructuring, and template literals. Learn about asynchronous JavaScript, including Promises and async/await, as these are frequently used in React applications. Be ready to explain how these JavaScript concepts integrate with React.
3. Sharpen Your Problem-Solving Skills: Infosys values candidates who can think logically and solve coding problems efficiently. Practice coding challenges, especially those involving DOM manipulation and data handling. Be prepared to walk through your approach, explain your decisions, and debug live if needed.
4. Review Projects and Codes: Be ready to discuss your previous React projects in detail. Focus on challenges you overcame, how you applied React concepts, and any performance or usability improvements you made. Show that you not only know how to use React but also how to solve real-world problems with it.

Conclusion

The Infosys React interview questions demand candidates to master essential React knowledge about fundamentals, state management strategies, and performance enhancement principles. Practicing code problems, highlighting your expertise in solving them, and talking about past work projects with confidence can all greatly increase your chances of success. Candidates who are strong in both basic JavaScript and advanced React concepts tend to stand out during the interview process. Check out how to get an internship at Infosys for the essential steps and required skills to help you increase your chances.

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