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Frontend Engineer

Technology and Engineering · #10 in series

Frontend Engineer interview prep

Top 100 interview questions for Frontend Engineer — modeled on real FAANG loops.

100

Questions

10

Topics

20

Free

HTML/CSS JavaScript React Frameworks/Libraries Web Performance Security Tools/Build Systems Testing Miscellaneous Behavioral/Soft Skills

HTML/CSS

10 questions

What is the difference between block and inline elements?

How does CSS specificity work?

What is the CSS box model, and how does it influence layout?

Explain the concept of responsive design.

How can you implement a grid system in CSS?

What are CSS preprocessors, and why would you use them?

How do you optimize web fonts for performance?

What are pseudo-elements and how do you use them?

Explain the difference between `visibility: hidden` and `display: none`.

How do you ensure cross-browser compatibility with CSS?

JavaScript

10 questions

Explain the concept of closures in JavaScript.

What is the difference between `let`, `var`, and `const`?

How do you handle asynchronous operations in JavaScript?

mediumbehavioral

What are promises and how do they work?

Can you explain the event delegation model?

What is the purpose of `use strict`?

How does prototypal inheritance work in JavaScript?

Explain the concept of "hoisting" in JavaScript.

What is the difference between `==` and `===`?

How do you prevent memory leaks in JavaScript?

React

10 questions

What are the differences between functional and class components?

How does React handle state management?

What are Hooks, and can you name a few commonly used ones?

Explain the concept of virtual DOM.

How do you optimize performance in a React application?

What is the role of keys in React?

How do you handle forms in React?

What is server-side rendering, and how does it work with React?

How do you manage global state in React applications?

What is the context API in React?

Frameworks/Libraries

10 questions

Explain the differences between Angular and React.

When would you choose Vue.js over other frameworks?

What is the purpose of Redux in a React application?

How does the Angular dependency injection system work?

What are the benefits of using TypeScript with Angular?

Describe the lifecycle of a Vue component.

What is the purpose of a service worker in a PWA?

How do you optimize a Vue.js application for performance?

What are the pros and cons of using a CSS-in-JS library?

How do you manage state in large-scale applications with React or Angular?

Web Performance

10 questions

How do you measure the performance of a web application?

What techniques do you use to reduce the load time of a web page?

How does lazy loading work?

What are the core web vitals, and why are they important?

How can you optimize images for the web?

What is a Content Delivery Network (CDN)?

Explain the concept of code splitting.

How do you defer the loading of non-essential JavaScript?

What are some ways to improve the time-to-first-byte (TTFB)?

How does caching work in web applications?

Security

10 questions

What is Cross-Site Scripting (XSS) and how do you prevent it?

How do you mitigate CSRF attacks?

What are the best practices for handling user authentication?

Explain the concept of Content Security Policy (CSP).

How do you ensure data is securely transmitted between client and server?

What is the importance of HTTPS?

How do you handle sensitive data in a frontend application?

What is CORS, and why is it important?

How do you protect against SQL injection?

What are security considerations when using third-party libraries?

Tools/Build Systems

10 questions

What is the role of Webpack in modern web development?

How do you configure Babel for a JavaScript project?

What are the differences between npm and Yarn?

How do you set up a development environment using Docker?

Explain the purpose of a task runner like Gulp.

How do you use ESLint to enforce code quality?

What is the purpose of a module bundler?

How do you implement continuous integration for a frontend project?

What are source maps, and how do they help in debugging?

How do you manage environment variables in a frontend application?

Testing

10 questions

What is the difference between unit testing and integration testing?

How do you set up a testing environment using Jest?

What is the role of end-to-end testing in web development?

Explain how to use React Testing Library.

What are the benefits of test-driven development (TDD)?

How do you mock API calls in tests?

What is snapshot testing?

How do you ensure accessibility in your tests?

What is the purpose of code coverage tools?

How do you handle flaky tests?

Miscellaneous

10 questions

What are the principles of RESTful APIs?

How would you structure a large-scale frontend application?

What is GraphQL, and how does it differ from REST?

Explain the concept of micro-frontends.

What are web components, and how do they work?

How do you handle internationalization in a web application?

What is the purpose of polyfills in JavaScript?

How do you perform code review effectively?

Explain the concept of "progressive enhancement."

How do you ensure your application is accessible to all users?

Behavioral/Soft Skills

10 questions

Describe a challenging technical problem you’ve faced and how you solved it.

How do you prioritize tasks when working on multiple projects?

Explain a situation where you had to work with a team to overcome a challenge.

How do you handle feedback or criticism of your work?

Describe a time when you had to learn a new technology quickly.

How do you manage conflicts within a team?

What motivates you to work in frontend development?

How do you stay updated with the latest trends in frontend technology?

Describe a project you are particularly proud of.

How do you ensure effective communication with non-technical stakeholders?

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