🚀 React Interview Experience (August 2025): Fulcrum (Part -1)

Overview

This document details a React developer interview experience that occurred in August 2025. The interview focused on core React concepts, best practices, and common front-end development challenges. The questions covered a wide array of topics, from component lifecycles to API integrations and authentication strategies.

Interview Rounds

The interview included questions on the following topics:

• React Component Lifecycle: The candidate was asked to explain the lifecycle of class components, including the mounting, updating, and unmounting phases and their associated methods.
• Functional Components and Hooks: Questions explored how functional components utilize hooks to manage lifecycle events, specifically useEffect for mounting, updating, and unmounting behaviors.
• Pure Components and Functions: The interviewer probed the candidate's understanding of pure components, which implement shouldComponentUpdate() with shallow prop and state comparisons, and pure functions, which produce the same output for the same input without side effects.
• React.memo: The discussion covered React.memo, a higher-order component that memoizes functional components to prevent unnecessary re-renders based on prop changes.
• useMemo vs. useCallback: The candidate was asked to differentiate between useMemo, which memoizes the result of a function, and useCallback, which memoizes the function reference itself.
• Backend API Communication: The interview addressed methods for communicating with backend APIs, including the use of fetch() and Axios, state management strategies, error handling, authentication, and optimization techniques like debouncing and caching.
• Fetch vs. Axios: The differences between the native fetch() API and the Axios library were discussed, including syntax, browser support, error handling, interceptors, timeout support, and progress tracking.
• Axios Interceptors: The interviewer inquired about Axios interceptors, which modify requests before they are sent or responses after they are received, and their use cases such as adding authentication tokens or handling errors globally.
• Authentication in React Apps: The conversation covered how to handle authentication in React applications, including storing tokens, attaching tokens to requests, protecting routes, managing authentication state, and implementing token refresh mechanisms.
• Routing in React JS: The use of React Router for implementing routing was discussed, including installation, component usage (BrowserRouter, Routes, Route, Link, Navigate), dynamic routing, nested routes, protected routes, and 404 handling.

Key Takeaways

• A strong understanding of React component lifecycles, both class-based and functional, is crucial.
• Knowledge of performance optimization techniques like React.memo, useMemo, and useCallback is essential for building efficient React applications.
• Proficiency in API communication using fetch() or Axios, along with proper error handling and authentication strategies, is expected.
• Familiarity with React Router for implementing routing and navigation is a must.
• Understanding the nuances between fetch() and Axios, as well as how to use Axios interceptors, demonstrates a deeper understanding of front-end development practices.