Web Development Interview Prep with 10 Questions You Should Expect

Employers are on the lookout for developers who are not only technically skilled but also adept at problem-solving and staying updated with the latest technologies.

To help you stand out in your next interview, we have compiled a list of 10 essential web development questions that frequently come up.

Originating from our vibrant community, we encourage professionals to contribute their questions and share insightful feedback.

1. What is CORS and How Does it Work?

Answer:

Cross-Origin Resource Sharing (CORS) is a security feature implemented by web browsers to manage how web applications interact with resources from different origins. It uses HTTP headers to dictate whether a browser should allow web applications running at one origin to access selected resources from a different origin.

For example, if a frontend application on https://frontend.com requests data from an API hosted on https://api.backend.com, the API server must include the appropriate CORS headers to allow the request. If these headers are not present or incorrect, the browser blocks the request to protect user data and prevent security risks such as Cross-Site Scripting (XSS) attacks.

2. Explain the Difference Between HTML5 and HTML4

Answer:

HTML5 introduced several new features and elements that were not available in HTML4, aimed at improving the user experience and providing better support for modern web development needs. Key differences include:

• New Semantic Elements: HTML5 added elements like <article>, <section>, <nav>, and <footer> to provide more meaningful structure to documents.

• Multimedia Support: HTML5 natively supports audio and video elements (<audio>, <video>) without requiring external plugins.

• APIs and Storage: HTML5 includes APIs for offline storage (localStorage and sessionStorage), canvas drawing (<canvas>), and more.

• Form Enhancements: New input types (e.g., email, date, number) and attributes (placeholder, required) were introduced to improve form handling.

Improved Accessibility: HTML5 focuses on making web content more accessible to users with disabilities by using ARIA (Accessible Rich Internet Applications) landmarks and roles.

3. What is a Progressive Web App (PWA)?

Answer:

A Progressive Web App (PWA) is a type of web application that uses modern web technologies to deliver an app-like experience to users. PWAs are designed to work on any device with a standard-compliant browser and provide several advantages:

• Offline Capability: Using service workers, PWAs can cache resources and function offline or with poor network connectivity.
• Responsive Design: PWAs are built to be responsive, adapting to different screen sizes and orientations.
• Installable: Users can install PWAs on their devices, adding them to the home screen for quick access, similar to native apps.
• Push Notifications: PWAs can send push notifications to re-engage users even when the browser is not open.
• Secure: PWAs are served over HTTPS to ensure secure data transmission and to prevent man-in-the-middle attacks.

4. Structure of a MIME Multipart Message

Answer:

A MIME multipart message allows combining multiple parts into a single message. Each part can have a different content type and is separated by boundaries defined in the header. Here’s an example structure:

Each section within the boundaries can represent different data types, such as text, images, or attachments, making MIME multipart messages versatile for transmitting complex data in a single request.

5. What is Long Polling and Its Drawbacks?

Answer:

Long polling is a technique used to simulate real-time communication in web applications. In long polling, the client makes an HTTP request to the server, which remains open until the server has new information to send. Once the server responds, the client processes the data and immediately opens a new request to wait for more updates. Drawbacks of long polling include:

• High Resource Consumption: Maintaining numerous open connections can strain server resources.
• Latency: Each request-response cycle introduces latency.
• Complexity: Implementing long polling requires careful handling of timeouts and reconnections.

WebSockets provide a more efficient alternative by establishing a persistent connection for real-time communication.

6. How Does the Fetch API Work in JavaScript?

Answer:

The Fetch API in JavaScript provides a modern way to make HTTP requests. It returns a promise that resolves to the Response object representing the response to the request. Here’s a basic example:

7. What is an ETag?

Answer:

An Entity Tag (ETag) is an identifier assigned by the web server to a specific version of a resource. ETags facilitate efficient caching and resource management by enabling clients to make conditional requests. When a client requests a resource, it includes the ETag value in the If-None-Match header. The server compares the ETag with the current version:

If the ETag matches, the server responds with a 304 Not Modified status, indicating the cached version is still valid. If the ETag does not match, the server sends the updated resource with a new ETag. This mechanism reduces bandwidth usage and speeds up page loads by avoiding unnecessary data transfers.

8. Stateless vs. Stateful Protocols

Answer:

HTTP is a stateless protocol, meaning each request from a client to server is independent and the server does not retain any session information between requests. Stateless protocols simplify server design and improve scalability since each request is self-contained.

In contrast, stateful protocols maintain the state across multiple interactions.

Examples include FTP and Telnet, where the server maintains a session state across multiple commands from the client. Stateful protocols can provide a more seamless user experience but require more complex server management to track and maintain session states.

9. What is a Content Delivery Network (CDN)?

Answer:

A Content Delivery Network (CDN) is a system of distributed servers that deliver web content to users based on their geographic location. CDNs improve load times, reduce latency, and increase availability by caching content on servers close to the end-users. Key benefits include:

Improved Performance: Reduced latency and faster load times due to proximity of servers.

Scalability: Ability to handle large amounts of traffic and distribute the load across multiple servers.

Reliability: Enhanced uptime and availability through redundant server locations.

Security: Protection against DDoS attacks and other security threats by absorbing and mitigating traffic spikes.

10. Differences Between GET and POST

Answer:

GET: Requests data from a specified resource. Parameters are appended to the URL, making them visible in the address bar. GET requests are idempotent and should not alter the server state. They are typically used for retrieving data.

POST: Submits data to be processed to a specified resource. Parameters are included in the request body, providing greater security for sensitive information. POST requests are not idempotent and can alter server state, making them suitable for creating or updating resources.

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