Interview Experience with EY as a React.js Frontend Engineer
Overview
This article details the interview process for a React.js Frontend Engineer position at Ernst & Young (EY). The interview assessed the candidate's proficiency in JavaScript, React.js, and general frontend development principles. The process aimed to evaluate the candidate's technical foundation, problem-solving capabilities, and understanding of best practices.
Interview Rounds
The interview process consisted of two technical rounds.
Technical Round 1: The Foundation Test
This virtual round focused on core JavaScript and React.js knowledge. The interviewer posed a combination of theoretical and coding questions to gauge the candidate's comprehension.
JavaScript Fundamentals
- The candidate was asked to explain the differences between variable declarations (
var,let,const) and function declarations (function declarations, function expressions, and arrow functions). - The candidate explained hoisting, bindings, and closures in JavaScript, providing examples of how
varand function declarations are hoisted. They discussed lexical scope and closures in depth.
React.js Essentials
- The candidate described how the React Virtual DOM enhances performance, explaining the diffing algorithm and reconciliation process and how React efficiently updates only the changed parts of the DOM.
- The candidate highlighted the advantages of using hooks and custom hooks in React, including cleaner code, stateful logic reuse, and performance improvements through
useMemoanduseCallback. - The candidate discussed the differences between functional and class components in React, addressing lifecycle methods vs. hooks, readability, performance improvements, and why React favors functional components.
- The candidate explained state management patterns, including
useState,useReducer, Context API, and external solutions like Redux or Zustand.
Optimization & Best Practices
- The candidate explained how keys help React identify elements efficiently and prevent unnecessary re-renders.
- The candidate outlined the lifecycle phases (Mounting, Updating, Unmounting) and their equivalent hooks (
useEffect,useLayoutEffect). - The candidate discussed techniques like memoization, lazy loading, code splitting, and avoiding unnecessary renders with
React.memo. - The candidate demonstrated how
useMemooptimizes computations,useCallbackmemoizes functions,useRefpreserves values across renders, anduseReducerhandles complex state logic. - The candidate discussed global state management, when to use Context API over Redux, and how it reduces prop drilling.
- The candidate discussed ARIA attributes, semantic HTML, keyboard navigation, and color contrast considerations.
JavaScript Coding Problems
The candidate solved coding challenges involving object manipulation, array transformations, and higher-order functions like map, filter, and reduce.
Technical Round 2: The On-Site Challenge
This round involved coding challenges, advanced React topics, and frontend performance optimizations.
Coding & Problem-Solving
- The candidate tackled more complex coding challenges, including recursion, asynchronous programming, and deep object cloning.
- The candidate built a React component with proper state management, context integration, and performance optimizations.
HTML & CSS
- The candidate discussed specificity, flexbox vs. grid, animations, BEM methodology, and performance optimizations like
will-change. - The candidate covered semantic HTML, lazy loading, preloading, and best practices for SEO.
Performance, Security & Tooling
- The candidate discussed how to improve application performance, avoid memory leaks, and enhance UX with efficient state management.
- The candidate engaged in a deep dive into event delegation, reconciliation process, and browser rendering optimizations.
- The candidate explored common security risks like XSS, CSRF, and best practices for securing React applications.
- The candidate discussed bundling, tree shaking, code splitting, and dependency management with NPM/Yarn.
Key Takeaways
- Master the Fundamentals: Solid JavaScript knowledge is essential for any frontend role.
- Deep Dive into React: Understanding React's internals is crucial, not just its usage.
- Performance & Optimization Matter: Employers highly value efficiency in code and UI.
- Security & Best Practices: Secure coding is just as crucial as writing functional code.
- Systematic Problem-Solving: Breaking down problems and approaching them logically is critical.
Original Source
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