Top 30 TCS ReactJs Interview Questions and Answers

Tata Consultancy Services (TCS) is a globally well-known IT services and consulting company. It offers various interesting job opportunities for technical professionals, including ReactJs developers. The company hires experienced ReactJs professionals having a thorough awareness of its ecosystem. The organization appreciates candidates with technical knowledge and the capacity to operate in group projects. The TCS interview process evaluates candidates who can support creative initiatives and drive team achievement. In this blog, we will cover some of the most commonly asked TCS ReactJs interview questions, sample responses, and advice to help you land the job.

TCS ReactJs Interview Questions for Freshers

TCS, one of the leading IT service providers, frequently hires ReactJs developers to join their innovative teams. Candidates have to answer technical interviews assessing their ReactJs’ skills and cultural fit as part of the hiring process. This section includes some of the commonly asked TCS ReactJs interview questions for freshers:

Q1. What is ReactJs, and why is it popular for front-end development?

Sample Answer: React JS is a JavaScript tool used to create user interfaces, particularly for single-page apps. It’s popular because of its component-based structure, which promotes reusability, and its use of the virtual DOM, which boosts performance by only updating parts of the user interface that change. React is the best choice since it can effectively manage big apps.

Q2. What are the main characteristics of ReactJS? 

Sample Answer: The main characteristics of React JS are: 

• Component-Based Architecture: This helps developers create encapsulated and reusable UI components, hence improving maintainability.
• Virtual DOM: It optimizes performance by only updating changed DOM components to maximize speed.
• JSX Syntax: It simplifies UI creation by allowing HTML within JavaScript
• Unidirectional Data Flow: It ensures consistent data flow, therefore facilitating debugging.

Q3. What are the differences between props and states in ReactJS?

Sample Answer: Props in React are read-only and passed from parent to child components to share data. On the other hand, a state is mutable and managed within a component to track changes. Props help make components reusable by providing dynamic values, whereas state allows components to handle user interactions and internal updates. While the parent controls props, the state is managed locally within the component.

Q4. What are React Hooks? Could you define some commonly used hooks?

Sample Answer: React hooks are features allowing state and lifecycle characteristics in functional components. Some of the commonly used hooks are:

• useState: It adds state to functional components
• Use effect: It runs side effects similar to data retrieval using Effect.
• useContext: It offers worldwide state access. Usually, hooks reduce the requirement for class components and streamline component management.

Q5. What is the purpose of the use of effects hook in React?

Sample Answer: React’s useEffect hook controls side effects including data fetching, subscriptions, and hand DOM modification. Based on its dependent array, it may be set to run under particular situations and follow the component’s renderings. Managing side effects in functional components would be difficult and ineffective without it.

Q6. What is the difference between a class component and a functional component in React?

Sample Answer: Class components are ES6 classes that extend ‘React.Component’, providing access to lifecycle methods and states. Their complexity calls for more boilerplate code. Conversely, functional components are simpler, mostly focused on UI rendering, and more efficient since they handle state and side effects via hooks.

Q7. How does React handle forms and user input?

Sample Answer: React handles forms and user input using controlled and uncontrolled components. In controlled components, React manages the input values through state (useState). It ensures real-time updates and validation. In uncontrolled components, form data is handled by the DOM itself using refs (useRef), making them useful for simpler or third-party integrations.

Q8. What is JSX? Why is it used in React?

Sample Answer: JSX (JavaScript XML) is a syntax extension that allows writing HTML-like code inside JavaScript. React uses it to create UI components and make them more readable and declarative. It simplifies development by combining HTML structure with JavaScript logic, making code easier to write and maintain.

Q9. How does the Virtual DOM of React work?

Sample Answer: React’s Virtual DOM is a lightweight copy of the real DOM that helps optimize rendering. When the state or props change, React updates the Virtual DOM first, compares it with the previous version (diffing), and then updates only the changed parts in the real DOM (reconciliation). This process leads to faster updates and improves app performance by minimizing direct DOM manipulations.

Q10. What is the use of the ‘key’ prop in React?

Sample Answer: React uses the ‘key’ prop to specifically identify elements in a list or array while delivering them. Using this, react tracks updated, added, or deleted objects so that it can quickly refresh the user interface. React’s performance depends on the ‘key’ prop as it guarantees that just the required items are re-rendered instead of the whole list.

Also Read: ReactJs Coding Interview Questions

TCS ReactJs Interview Questions for Mid-Level Experienced Candidates

TCS hires skilled ReactJs developers, especially those with solid experience who can contribute to their innovative projects. The interview procedure for candidates at the mid-level emphasizes advanced React ideas, problem-solving, and practical application development. This section includes some typical TCS ReactJs interview questions meant for mid-level applicants.

Q11. What is the importance of keys in React? What meaning do they carry?

Sample Answer: React’s keys are necessary for effectively updating and rendering list components. By reducing pointless re-renders, they enable React to find which objects have changed, been added, or deleted, therefore boosting performance. React’s unique keys help track items and improve UI consistency during dynamic updates.

Q12. Describe the difference between controlled and uncontrolled components in React.

Sample Answer: Controlled components in React manage their state through props and ‘useState’. It ensures React controls the input values. On the other hand, uncontrolled components rely on the DOM to handle the state using ‘refs’ (useRef) instead of the React state. Use controlled components for better control and validation, while uncontrolled components work well for simpler use cases like integrating with third-party libraries.

Q13. How does React‘s context API work? When can you use it?

Sample Answer: React’s Context API works by allowing data to be shared across components without prop drilling. It creates a central store where a ‘Provider’ wraps components, making the data available, and a ‘Consumer’ or ‘useContext’ hook retrieves it. Use it when multiple components need access to shared data like themes, authentication, or global settings.

Q14. Can you explain how React handles component lifecycle methods?

Sample Answer: React uses lifecycle techniques to oversee the life cycle of a component from manufacture to disposal. Common lifetime techniques in class components include ‘componentDidMount’, ‘componentDidUpdate’, and ‘componentWillUnmount’. The effect hook helps conduct side effects at designated points during the functional components’ lifetime. 

Q15. How would you implement client-side routing in a React application?

Sample Answer: Client-side routing in a React application is typically implemented using React Router, a popular library for handling navigation. React Router allows you to define different routes within your application that map to specific components or views. 

By using components like <BrowserRouter>, <Route>, and <Link>, you can create a single-page application where the URL changes based on the user’s navigation without reloading the page. The <Switch> component can be used to render the first matching route, providing a smooth, seamless navigation experience. 

Pro Tip: Aiming for a job at TCS? Explore our guide on the TCS HR Interview Questions and Answers to ace the selection process for the role.

Q16. How do you manage the application errors in React?

Sample Answer: React catches JavaScript mistakes in components using error boundaries, logs those mistakes, and shows a fallback UI. React can manage mistakes and stop the whole application from failing. It applies the ‘componentDidCatch’ lifecycle approach in class components.

Q17. Explain what a React router is. How would you utilize it in a React application?

Sample Answer: React Router is a library that enables navigation and dynamic routing in a React application. It lets you define different routes and render specific components based on the URL, creating a seamless single-page app experience. To use it, wrap your app with ‘BrowserRouter’, define routes using ‘Route’ and ‘Switch’ (or Routes in newer versions), and use ‘Link’ or ‘useNavigate’ for navigation.

Q18. Describe the process of reconciliation in React.

Sample Answer: Reconciliation in React updates the UI efficiently when the state or props change. React compares the new virtual DOM with the previous one using a diffing algorithm and updates only the changed parts in the actual DOM. This makes rendering faster and smoother, keeping the app responsive without unnecessary re-renders.

Q19. How does React’s ‘useRef’ hook work? What are some use cases?

Sample Answer: The useRef hook in React is used to persist values across renders without causing a re-render when the value changes. It is frequently used to hold mutable variables unrelated to the render cycle of the component or to refer directly to DOM elements. ‘useRef’ allows you, for instance, to access a DOM element to store values like timers, counters, or previous state values.

Q20. What is the purpose of the ‘useEffect’ hook in functional components?

Sample Answer: The ‘useEffect’ hook in React lets functional components handle side effects like fetching data, updating the DOM, or setting up subscriptions. It runs after the component renders and can be controlled with dependencies to run only when needed. It helps manage tasks that happen outside the normal UI flow, keeping your app responsive and efficient.

TCS ReactJs Interview Questions for Experienced Candidates

For experienced ReactJs developers, TCS looks for proficiency in advanced React concepts, problem-solving skills, and the ability to handle large-scale applications. The interview procedure is meant to evaluate the knowledge of technical concepts and practical experience in actual project management. This section will include some TCS ReactJs interview questions for experienced candidates to assist you in your preparation.

Q21. Explain the virtual DOM of React and its mechanism.

Sample Answer: React’s virtual DOM is a lightweight replica of the real DOM. React initially updates the virtual DOM, compares it with the prior version, and then implements the required modifications to the actual DOM when changes take place. This method reduces direct manipulation of the real DOM, leading to higher efficiency.

Q22. How can you handle state management in a large React application?

Sample Answer: State management in a large React application can be handled using centralized state management libraries like Redux, Zustand, or Recoil. These libraries help manage complex state logic, share data across components, and optimize performance by preventing unnecessary re-renders. Context API with ‘useReducer’ can also be used for moderate state management needs. However, dedicated libraries offer better scalability and debugging tools for large-scale applications.

Q23. How do React hooks vary from class component lifecycle techniques?

Sample Answer: React hooks provide a functional way to manage state and side effects, replacing class component lifecycle methods. Instead of using methods like ‘componentDidMount’ or ‘componentDidUpdate’, hooks like ‘useState’ and ‘useEffect’ handle state and side effects in functional components directly. Hooks make code more concise, reusable, and easier to understand than class-based lifecycle techniques.

Q24. What is the role of ‘shouldComponentUpdate’ in React JS?

Sample Answer: ‘shouldComponentUpdate’ is a lifetime approach in class components. It decides if the component should re-render depending on changes to state or props. Since it avoids pointless re-renders, it is utilized for performance optimization. 

Q25. How can you improve the performance of a React application? 

Sample Answer: Here are some of the ways to improve the performance of a React JS application:

• Optimize rendering and reduce unnecessary re-renders. 
• Use ‘React.memo’ for component memoization.
• Implement ‘useCallback’ and ‘useMemo’ to optimize function and value references and lazy loading with React’s ‘React.lazy’ and ‘Suspense’ to load components only when needed. 
• Optimize large lists with React’s virtualization techniques (e.g., react-window), minimize state updates, and use production builds for better efficiency.

Q26. What is React’s Context API? When should you use it?

Sample Answer: React’s Context API allows you to manage and share state globally without prop drilling. It is useful when multiple components need access to the same data, such as themes, authentication, or user preferences. You should use it when passing props through multiple layers becomes complex. However, avoid overusing it for frequently changing state, as it may cause unnecessary re-renders.

Q27. How would you implement server-side rendering (SSR) in React?

Sample Answer: React’s server-side rendering (SSR) can be implemented with ‘Next.js’ among other frameworks. The server presents the React components to HTML using SSR before forwarding them to the browser. This method enhances the first-page load’s performance and helps with technical SEO to quickly access the material.

Q28. Explain the concept of higher-order components (HOCs) and their use.

Sample Answer: Higher-order components (HOCs) are functions that transform one component into a new one with more characteristics. They improve components without changing their original structure and make the code reusable. HOCs are used for component logging behavior, data retrieval, and authentication checks.

Q29. What is the difference between ‘useEffect’ and ‘useLayoutEffect’?

Sample Answer: Both the ‘useEffect’ and ‘useLayoutEffect’ hooks in React. The key difference between ‘useEffect’ and ‘useLayoutEffect’ is when they execute. useEffect runs asynchronously after the render is committed to the screen. Thus making it suitable for side effects like data fetching. useLayoutEffect runs synchronously after the DOM updates but before the browser paints, which makes it easier to measure DOM elements or apply visual updates without flickering.

Q30. How can you handle React’s form validation?

Sample Answer: In React, form validation is handled using controlled components with ‘useState’ to track input values. Validation is performed by checking required fields, data types, and custom conditions. After validation, form submissions are managed, and user-friendly error messages are displayed when necessary. Libraries like React Hook Form or Formik can simplify and optimize the validation process.

Preparation Tips for TCS ReactJs Interview Questions 

Familiarity with the basic values and best practices is crucial to ace the TCS React JS interview questions. The company hires professionals to support various projects. Here are some tips that will help you prepare your strategies to guide your success:

• Master React Fundamentals: Ensure you have a strong knowledge of React concepts including components, state, props, and the virtual DOM. Candidates should be experts in these fundamental skills.
• Understand React Hooks Completely: Know how to use the react jooks such as ‘useState’, ‘useEffect’, ‘useContext’, and ‘useMemo’. TCS prefers individuals who can manage lifecycle techniques with hooks and are strong in functional components.
• Be Comfortable with State Management: Knowing how to manage a state is essential, whether React Context, Relic, or any other state management tool. Be prepared for questions about managing big-scale state-run projects as well.
• Focus on Performance Optimization: TCS emphasizes developing effective and high-performance React apps for performance optimization. Discover methods like lazy loading, code-splitting, and memoizing to talk about approaches to raise app speed during your interview.
• Practice Real-World Scenarios: TCS often asks about practical use cases, so practice solving common challenges like form handling, routing, and error boundaries. You can use instances from your past work or projects, to highlight your ability to solve problems.

Conclusion 

Preparing for the TCS ReactJS interview questions requires a strong grasp of basics, advanced concepts, and practical implementation. Mastery of fundamental skills including components, hooks, state management, and performance optimization will enable candidates to answer questions for different expertise levels. Practicing the common interview questions and proving your problem-solving ability will help to guarantee success in landing a job at TCS. You should also stay current with React’s new features to ace the interview.

Check out our blog on the top React JS interview questions and answers and prepare well for your next interview.

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