🚀 React Interview Experience (August 2025): L & T(Part -1)

Overview

This document outlines the interview experience for a React Developer position at L & T (Larsen & Toubro) in August 2025. The interview focused on core React concepts, JavaScript fundamentals, state management, performance optimization, error handling, and design patterns. The candidate's responses provide a valuable resource for developers preparing for similar roles.

Interview Rounds

The interview process included questions covering a range of frontend development topics:

React Fundamentals:

• Question 1: What is React, and how does it compare to other tools?
  • The candidate correctly defined React as an open-source JavaScript library for building user interfaces, emphasizing its component-based architecture, virtual DOM, unidirectional data flow, strong ecosystem, and JSX syntax.
• Question 2: Can you elaborate on component-based architecture?
  • The candidate explained the principles of component-based architecture, including encapsulation, reusability, composability, and maintainability.
• Question 3: What are React Hooks?
  • The candidate accurately described React Hooks as functions that enable the use of state and other React features in functional components, highlighting useState, useEffect, useContext, useRef, useMemo, and useCallback.
• Question 4: How do you handle state management?
  • The candidate detailed different state management approaches based on application complexity, including local state (useState, useReducer), global state (Context API, Redux, Zustand), server state (React Query), and URL state (React Router).
• Question 5: In order to optimize performance, how can you achieve it in React?
  • The candidate outlined various optimization techniques, including memoization (React.memo, useMemo, useCallback), lazy loading & code splitting (React.lazy, Suspense), efficient lists (key props, windowing), avoiding reconciliation, batched updates (React 18+), and the use of React DevTools Profiler.

JavaScript Fundamentals:

• Question 6: Write a function to reverse a string.
  • The candidate provided two solutions: one using built-in methods and another without, demonstrating a strong understanding of string manipulation.
• Question 7: How do you handle errors?
  • The candidate described error handling strategies for synchronous code (try-catch), asynchronous code (.catch() in Promises, try-catch in async-await), React components (Error Boundaries), logging (Sentry, LogRocket), validation, and fallback UI.
• Question 8: Can you add error handling in the reverse string function?
  • The candidate enhanced the reverseString function with error handling, including type checking and a try-catch block.

Design Patterns:

• Question 9: Have you worked on design patterns?
  • The candidate cited experience with the Singleton, Factory, Observer, Strategy, HOC & Render Props, and Module patterns.
• Question 10: What is the Factory pattern?
  • The candidate explained the Factory Pattern as a creational design pattern for creating objects without specifying the exact class. They provided a JavaScript example and a React-specific use case with button components.

Key Takeaways

• A strong understanding of React fundamentals is crucial, including components, hooks, and state management.
• Knowledge of performance optimization techniques is essential for building efficient React applications.
• Experience with error handling strategies is vital for creating robust and user-friendly applications.
• Familiarity with common design patterns improves code quality, reusability, and maintainability.
• Being able to articulate solutions with and without built-in methods showcases a deeper understanding of the underlying logic.