Gautam Makavana

Essential Front-End Interview Topics Explained

Gautam Makavana's photo
Gautam Makavana
·

2 min read

Essential Front-End Interview Topics Explained
  1. What is the difference between null and undefined in JavaScript?

  • null is an explicitly assigned value that represents the absence of any value.

  • undefined is a variable that has been declared but has not been assigned a value.

  1. What is the purpose of the defer attribute in the <script> tag?

    The defer attribute tells the browser to download the script while parsing the HTML but execute it only after the HTML parsing is complete.

  2. What is the purpose of the async attribute in the <script> tag?

    The async attribute tells the browser to download the script in the background without blocking HTML parsing, and it will execute the script as soon as it's downloaded.

  3. Explain the concept of CORS (Cross-Origin Resource Sharing).

    CORS is a security feature implemented by web browsers that restricts web pages from making requests to a different domain than the one that served the web page. It ensures better security for web applications.

  4. What is the fetch() API in JavaScript?

    The fetch() API is used to make network requests, typically to fetch resources from a server. It returns a promise that resolves to the Response object representing the response to the request.

  5. What are Web Components?

    Web Components are a set of web platform APIs that allow you to create reusable custom elements with their own encapsulated HTML, CSS, and JavaScript.

  6. What is Event Bubbling and Event Capturing in the DOM?

  • Event Bubbling: When an event is triggered on a DOM element, it first fires on that element, then on its parent, and so on, propagating up the DOM tree.

  • Event Capturing: The opposite of event bubbling, where the event is captured at the topmost parent element and then propagates down to the target element.

  1. What is the significance of z-index in CSS?

    The z-index property is used to control the stacking order of elements. Elements with higher z-index values will be displayed above elements with lower values.

  2. How do you optimize website performance?

    Performance optimization can involve various techniques, such as:

  • Minifying and compressing CSS, JavaScript, and images.

  • Using responsive images and lazy loading.

  • Reducing HTTP requests and using caching.

  • Implementing server-side rendering or code-splitting for faster initial loading.

  • Optimizing database queries and server code.

HTML5CSSJavaScriptNode.jsReact