Top 30 Frontend Developer Interview Questions & Answers for 2 Years of Experience – 2025

As a frontend developer with two years of experience, you are expected to have solid knowledge of HTML, CSS, JavaScript, and frameworks like React, Angular, or Vue.js. You should also be proficient in responsive design, version control, and debugging tools. Here's a list of 30 interview questions that are commonly asked for frontend developer positions with two years of experience, along with ideal answers tailored for 2025.

Basic Frontend Development Questions

• 1. What is the difference between HTML, CSS, and JavaScript?
  HTML is used to structure content on the web, CSS is used for styling, and JavaScript is used to add interactivity and dynamic behavior.
• 2. What is the purpose of the alt attribute in an <img> tag?
  The alt attribute provides alternative text for an image if it cannot be displayed, improving accessibility and SEO.
• 3. Explain the concept of the box model in CSS.
  The box model consists of content, padding, border, and margin, and defines how elements are displayed and how space is calculated around them.
• 4. What are media queries in CSS?
  Media queries allow CSS to be applied based on the device's characteristics, such as screen size or resolution, enabling responsive design.
• 5. What is the difference between == and === in JavaScript?
  == compares values with type coercion, while === compares both value and type, making it more strict.

JavaScript & Frameworks

• 6. What are promises in JavaScript?
  A promise is an object representing the eventual completion or failure of an asynchronous operation. It allows chaining of asynchronous code.
• 7. Explain the concept of closures in JavaScript.
  A closure is a function that retains access to its lexical scope, even when the function is executed outside of that scope.
• 8. What are the differences between let, const, and var?
  let and const are block-scoped and have better scoping behavior than var, which is function-scoped.
• 9. How does this work in JavaScript?
  this refers to the context of the function execution. It can change depending on how the function is called.
• 10. What is the virtual DOM in React?
  The virtual DOM is an in-memory representation of the real DOM elements. React compares the virtual DOM to the real DOM to efficiently update only the necessary parts.

React & Other Frontend Libraries/Frameworks

• 11. What is JSX in React?
  JSX is a syntax extension for JavaScript that allows you to write HTML-like code within JavaScript, making React components easier to write and read.
• 12. What is state and props in React?
  State is an object that holds the data that changes over time within a component, while props are read-only data passed from a parent component.
• 13. How do you handle events in React?
  In React, events are handled using camelCase syntax, such as onClick, and are passed as functions in JSX.
• 14. What are lifecycle methods in React?
  Lifecycle methods are hooks that allow developers to run code at different stages of a component's lifecycle (e.g., componentDidMount(), componentWillUnmount()).
• 15. What is Redux, and how does it work in React?
  Redux is a state management library that allows for centralized state management across an entire application. It uses actions and reducers to update the state.

Version Control & Build Tools

• 16. How does version control work with Git?
  Git tracks changes to files, allows multiple developers to collaborate, and maintains version history. Commands like git commit, git push, and git pull are used for version control.
• 17. What is the difference between git pull and git fetch?
  git fetch downloads new changes from the remote repository but doesn't merge them, while git pull fetches and automatically merges them.
• 18. What is Webpack, and how does it work?
  Webpack is a module bundler that bundles JavaScript files, CSS, images, and other assets for efficient browser loading.
• 19. What is Babel?
  Babel is a JavaScript compiler that allows you to write modern JavaScript (ES6+) and transpile it into backward-compatible JavaScript for older browsers.
• 20. What is the purpose of npm?
  npm (Node Package Manager) is used for managing JavaScript libraries and dependencies in a project.

Performance and Debugging

• 21. How do you optimize performance in React?
  You can optimize performance in React by using techniques like memoization, lazy loading components, and avoiding unnecessary re-renders using React.memo() and useMemo().
• 22. How do you handle cross-browser compatibility issues?
  To handle cross-browser issues, use CSS resets, feature detection libraries like Modernizr, and test your application in different browsers.
• 23. What tools do you use for debugging in JavaScript?
  I use browser developer tools, console.log(), breakpoints, and sometimes third-party tools like Sentry for debugging JavaScript code.
• 24. What is the difference between synchronous and asynchronous code?
  Synchronous code runs sequentially, blocking the execution until it completes, while asynchronous code allows other operations to run concurrently without waiting for the previous one to finish.
• 25. What is the purpose of the debounce and throttle functions?
  debounce limits the rate at which a function can fire, while throttle ensures the function is called at a fixed rate.

CSS and Design

• 26. What is Flexbox, and when would you use it?
  Flexbox is a CSS layout model that allows items within a container to be dynamically arranged in a one-dimensional layout (rows or columns).
• 27. What is the difference between absolute, relative, and fixed positioning in CSS?
  absolute positions an element relative to its nearest positioned ancestor, relative positions an element relative to its normal position, and fixed keeps an element fixed to the viewport.
• 28. What is a CSS Grid Layout?
  CSS Grid Layout provides a two-dimensional grid system for creating complex layouts, with both rows and columns.
• 29. What is the difference between a class and an ID in CSS?
  A class is reusable and can be applied to multiple elements, while an ID is unique and should be used for only one element on a page.
• 30. How do you implement responsive design?
  By using CSS media queries, flexible grid layouts, and fluid images that adapt to various screen sizes.