Question: What is the Document Object Model (DOM) in HTML?
Answer: The DOM is a programming interface for HTML and XML documents. It represents the page so that programs can change the document structure, style, and content.
Question: How do you optimize website performance?
Answer: Optimize images, minimize CSS and JavaScript, use a Content Delivery Network (CDN), and leverage browser caching.
Question: Explain the difference between == and === in JavaScript.
Answer: == compares values after type coercion, while === compares both value and type, which is why === is recommended for accuracy.
Question: What are CSS preprocessors, and why use them?
Answer: CSS preprocessors like SASS or LESS extend CSS with variables, nested rules, and functions, making CSS more maintainable and easier to write.
Question: How do you ensure your website’s design is mobile-friendly?
Answer: Use responsive design techniques, like flexible grids, flexible images, and media queries.
Question: Can you explain what ARIA and screen readers are?
Answer: ARIA stands for Accessible Rich Internet Applications and helps make web content more accessible to people with disabilities. Screen readers are software that helps visually impaired users navigate and read content.
Question: What is the purpose of a CDN, and how does it work?
Answer: A CDN delivers content faster by caching it in multiple locations around the world, so it’s closer to the user.
Question: How do you handle browser-specific styling issues?
Answer: Use CSS resets, vendor prefixes, feature detection, and conditional comments for IE.
Question: What is a Promise in JavaScript?
Answer: A Promise is an object representing the eventual completion or failure of an asynchronous operation.
Question: What are web components?
Answer: Web components are a set of web platform APIs that allow you to create new custom, reusable, encapsulated HTML tags.
Question: What is the difference between localStorage, sessionStorage, and cookies?
Answer: localStorage persists until explicitly deleted, sessionStorage is cleared when the session ends, and cookies are sent to the server with each request.
Question: How would you implement a feature that requires data from a server?
Answer: Use AJAX or Fetch API to request data from the server asynchronously.
Question: Explain event delegation in JavaScript.
Answer: Event delegation is a technique of handling events efficiently by adding an event listener to a parent element instead of multiple child elements.
Question: What is a CSS BEM?
Answer: BEM stands for Block Element Modifier. It’s a methodology that helps you to create reusable components and code sharing in front-end development.
Question: What are service workers?
Answer: Service workers act as a proxy between web applications, the browser, and the network, enabling offline experiences, background sync, and push notifications.
Question: How do you ensure accessibility in a web application?
Answer: Use semantic HTML, ensure keyboard navigability, use ARIA roles where necessary, and follow WCAG guidelines.
Question: What are some ways to reduce page load time?
Answer: Minimize HTTP requests, optimize images, asynchronous loading of CSS and JavaScript, and reduce server response time.
Question: How do you handle version control?
Answer: Use version control systems like Git, and follow best practices like frequent commits and branching strategies.
Question: What is cross-site scripting (XSS), and how do you prevent it?
Answer: XSS is a security vulnerability that allows attackers to inject malicious scripts. Prevent it by sanitizing user input and using Content Security Policy (CSP).
Question: Explain the concept of a RESTful API.
Answer: RESTful API is an API that follows REST (Representational State Transfer) principles, providing a way to interact with web services in a stateless manner.
Question: How do CSS Flexbox and Grid differ?
Answer: Flexbox is a one-dimensional layout method for laying out items in rows or columns. Grid is a two-dimensional layout system for rows and columns.
Question: What are some SEO best practices for web development?
Answer: Use semantic HTML, ensure fast load times, optimize for mobile, and use descriptive URLs and meta tags.
Question: How do you ensure your code is maintainable and scalable?
Answer: Write clean, modular code, document it well, and adhere to design patterns and best practices.
Question: What tools do you use for testing and debugging?
Answer: Use browser dev tools, testing frameworks like Jest or Mocha, and debugging tools like Chrome DevTools