Programs
Today, we can see almost every person connected to technology, who uses online platforms for their daily tasks. Hence, one of the most significant areas for building and maintaining websites or mobile applications can be done through web development. Today, the need for highly skilled developers is constantly rising as almost all new startups prefer online platforms. Therefore anyone preparing for the web developer interview process, either fresher or any candidate having experience, must have in-depth knowledge of web development along with multiple technologies and best practices.
In this blog, we will see the core concepts and the top web developer interview questions and answers (2024). We will discuss what a web developer focuses on the most and explanation for specific queries asked in the interview. This also includes behavioural questions which are necessary for both freshers and experienced professionals so that one can succeed in their next job interview.
The basic role of any web developer is to address website-related queries, which can occur during website building and maintenance. They implement website structure, design, and functionality features using tools and programming languages. Website developers make sure that the sites they create are not only beautiful but also work well on diverse devices/browsers. Web developers bring an artistic vision of designers into the websites we see or the applications we use daily. The code written by any web developer should meet every standard so that the final interface is user-friendly and visually appealing, containing all running interactive elements.
Web designers play an essential role in the digital industry, as they have to ensure the operational websites are running without any conflict, preserving all the user-friendly interfaces. Duties may vary depending on several specialisations in web development.
These are just different roles needed for creating & maintaining efficient, safe & user-friendly sites.
HTML (HyperText Markup Language) is the standard language used to create web pages. HTML provides us with some important basic structures which can be used to develop the website. Elements like headings, links, titles, paragraphs, images, etc. can be added to the website using HTML.
CSS (Cascading Style Sheets) is a language used to style and layout web pages. It does this by controlling style-related aspects like the layout as well as variations in the display based on factors such as colours or spacing of the text and other content.
HTML tags represent the basics of HTML. They help in defining and ordering web page content. Some examples of HTML tags are text headings, paragraphs, images and hyperlinks.
| Aspect | HTML | XHTML |
| Syntax | Flexible, less strict | Strict, follows XML rules |
| Doctype | Optional, can be omitted | Mandatory, must be declared |
| Closing Tags | Optional for some elements | Required for all elements |
| Case Sensitivity | Not case-sensitive | Case-sensitive |
| Error Handling | Browsers can auto-correct errors | Must be error-free, no auto-correction |
CSS selectors are patterns used to select and style specific HTML elements. They allow us to target elements based on their attributes (like class, id, or type) so that we can apply styles across our site without repeating ourselves too much.
| Aspect | Block-Level Element | Inline Element |
| Display | Takes up the full width of its container | Takes only as much width as needed |
| Starts on a New Line | Yes | No |
| Examples | <div>, <p>, <h1> | <span>, <a>, <img> |
A well-known programming language which can add interactivity on web pages, allowing us to create different real-time dynamic content to attract more and more users. It benefits in growing more user-friendly and interesting websites so that people can easily understand, and not get bored of using the same website or mobile application again. JavaScript includes animations, form validation, interactive features, dynamic randomness with time, video playback, caching, etc. enhancing overall user experiences.
| Scope Type | Description | Example |
| Global Scope | Variable accessible anywhere in the code | var globalVar = “I am global”; |
| Function Scope | Variable accessible only within a function | javascript function myFunc() { var localVar = “I am local”; } |
| Block Scope | Variable accessible only within a block (curly braces) | javascript if (true) { let blockVar = “I am block-scoped”; } |
HTTP cookies are nothing but small chunks of data stored on browsers or any mobile applications, especially when a user interacts with the platform. Hence, cookies may include login credentials, shopping cart contents, website settings (other than default), quick recommendations, etc. Cookies help websites provide a personalised experience for users by remembering their activities and preferences across visits.
| Aspect | Class Selector (.) | ID Selector (#) |
| Usage | Used to style multiple elements | Used to style a single unique element |
| Syntax | . followed by class name | # followed by ID name |
| Priority | Lower specificity | Higher specificity |
The DOM (Document Object Model) is a programming interface for web documents. We can say this is a document which represents the structure of any webpage as a tree of objects. Hence, this allows developers to interact and manipulate HTML and CSS. Using the DOM, developers can dynamically change the content, structure, and style of a webpage in response to user interactions or other events.
JavaScript promises are objects used for asynchronous operations. They represent the eventual completion (or failure) of an operation and its resulting value. Promises have three states: pending, fulfilled, and rejected.
Here’s a simple example of a JavaScript promise:
| Aspect | == (Abstract Equality) | === (Strict Equality) |
| Type Coercion | Performs type conversion if necessary | No type conversion, checks both value and type |
| Usage Example | 5 == ‘5’ (true) | 5 === ‘5’ (false) |
| Common Use Case | General equality check | Precise equality check, recommended |
| Aspect | var | let | const |
| Scope | Function-scoped | Block-scoped | Block-scoped |
| Reassignment | Can be reassigned | Can be reassigned | Cannot be reassigned |
| Hoisting | Hoisted with undefined value | Hoisted but not initialised | Hoisted but not initialised |
| CSS Type | Location | Use Case |
| Inline CSS | Directly within the HTML element using the style attribute | Quick, one-time style changes to a single-element |
| Internal CSS | Within the <style> tag in the HTML <head> | Styling a single page with specific styles |
| External CSS | In a separate .css file | Applying consistent styles across multiple pages |
Frontend development has all the development prerequisites to make an interface of any website or mobile application, which can be directly seen by the users. It Includes tasks like designing layouts, templates, responsive designs, and cross-browser compatibility. Front-end developers use languages like HTML, CSS, and JavaScript to build user interfaces and improve user experience.
| Aspect | Responsive Design | Adaptive Design |
| Layout | Fluid layout that adapts to screen size | Fixed layouts for specific breakpoints |
| Flexibility | Highly flexible, one design for all | Separate designs for different devices |
| Development | Requires one flexible design | Requires multiple designs |
| Performance | May load slower due to the fluid layout | Faster as only necessary assets are loaded |
All the server-side work is done in backend development. Web developers must include logic designing, database implementation, server configurations, and all the other tasks which directly or indirectly connect to the front-end elements. They use languages like Python, Java, and SQL to build the backend infrastructure that powers the front end.
A Doctype in HTML is a declaration that informs the web browser about the version of HTML the page is written in. It ensures that the browser renders the page correctly. The Doctype is placed at the very top of an HTML document. Here’s an example:
In modern web development, <!DOCTYPE html> is commonly used to trigger standards mode, ensuring that the browser renders the page according to the latest HTML specifications.
| Aspect | SASS | LESS |
| Syntax | Uses indented syntax (optional) or SCSS | Uses syntax similar to CSS |
| Features | Advanced features like loops, conditions | Fewer features, simpler syntax |
| Compatibility | Requires Ruby or Node.js | Works directly with Node.js |
| File Extension | .scss or .sass | .less |
Semantic HTML uses meaningful tags to define the structure and content of a webpage. Tags like <header>, <footer>, <article>, and <section> clearly describe their purpose, improving accessibility and SEO by allowing search engines and screen readers to better understand the content.
Child selectors in CSS are used to style elements that are direct children of a specified parent. They allow for more precise control over styling. Here’s an example:
The CSS box model consists of the following components:
| Data Type | Description | Example |
| String | Represents text | “Hello, world!” |
| Number | Represents numeric values | 42, 3.14 |
| Boolean | Represents true/false values | true, false |
| Object | Represents key-value pairs | { name: “Alice” } |
| Array | Represents ordered lists | [1, 2, 3] |
| Undefined | Variable with no assigned value | let x; |
| Null | Represents no value or empty object | null |
| Symbol | Represents unique identifiers | Symbol(“id”) |
| BigInt | Represents large integers | 9007199254740991n |
CSS3 transitions allow for smooth changes between different states of an element. Here are some key properties:
Pseudo-classes in CSS are used to define the special states of an element. They can style elements based on user interaction or position in the document tree. Here’s an example:
We can use media queries in CSS3 to apply several styles that are based on the characteristics of any device. This includes screen width, height and overall orientation of the screen of the user’s device, enabling overall responsiveness of the application to adapt to all devices. Here’s an example:
| Aspect | Block-Level Elements | Inline Elements |
| Display | Takes up the full width of its container | Takes only as much width as needed |
| Starts on New Line | Yes | No |
| Examples | <div>, <p>, <h1> | <span>, <a>, <img> |
We use the float property to position an element inside a container tag to move left or right, which can allow other content to wrap around it. Hence it has a very common use in creating layouts with images and texts. Here’s an example:
This feature in CSS is very similar to the layers used in Photoshop or any photo editing application. The z-index controls the order of elements along the z-axis and the stacking helps to either hide other elements underneath top layer elements or to overlay any other element. The higher the z-index value, the more prior it is displayed in front of elements with lower values.
| Aspect | window.onload | onDocumentReady |
| Timing | Fires after the entire page is loaded, including images and CSS | Fires as soon as the DOM is fully loaded, but before images and CSS are loaded |
| Usage | Suitable for initialising scripts that require full page load | Ideal for scripts that only need the DOM to be ready |
| Example | javascript window.onload = function() { console.log(“Page fully loaded!”); }; | javascript document.addEventListener(“DOMContentLoaded”, function() { console.log(“DOM ready!”); }); |
External style sheets are preferred because they allow for:
| Aspect | JavaScript Libraries | Vanilla JavaScript |
| Ease of Use | Simplifies DOM manipulation | Requires more code for the same tasks |
| Performance | May add overhead due to library size | Generally faster, no extra dependencies |
| Cross-Browser | Libraries like jQuery handle cross-browser issues | Developers must manually handle cross-browser compatibility |
| Learning Curve | Easier for beginners | Requires understanding core JavaScript concepts |
REST stands for Representational State Transfer, which we use to follow the principles while using RESTful APIs. Its design follows all these standards to create web services, using standard HTTP methods like GET, POST, PUT, and DELETE. The CRUD operation (Create, Read, Update, Delete) can be carried out using it. RESTful APIs are stateless, scalable, and designed to work with various data formats, such as JSON and XML.
Generally, we use WebSockets for real-time bidirectional communication, establishing a connection between a client and a server. It allows us for continuous data exchange over a single, long-lived connection, unlike any other HTTP, that is request-response-base. Therefore it is highly used in live chats, gaming and many applications which use real-time notifications.
| Popup Box | Description | Example |
| alert() | Displays a simple message to the user | alert(“This is an alert!”); |
| confirm() | Asks the user to confirm an action | confirm(“Are you sure?”); |
| prompt() | Asks the user to input some data | prompt(“Enter your name:”); |
Comments in JavaScript are used to explain code, making it easier to understand and maintain.
// This is a single-line comment
let x = 5; // Assign 5 to x
/* This is a
multi-line comment */
let y = 10;
| Variable Type | Description | Example |
| Undefined | A variable that has been declared but not assigned a value | let x; // x is undefined |
| Undeclared | A variable that has not been declared in the program | javascript console.log(y); // ReferenceError: y is not defined |
| Aspect | External CSS | Internal CSS |
| Location | In a separate .css file | Within a <style> tag in the HTML document |
| Reusability | Can be reused across multiple pages | Only applies to the specific HTML document |
| Performance | Improves load time due to caching | Increases load time as it’s embedded in the document |
Here, we can say different methods for bug testing like, initially understanding the overall code’s logic and flow, followed by using tools like Chrome DevTools to set breakpoints and steps throughout the code. You must constantly use console.log() statements to keep track of errors and variable values for perfect execution.
| Aspect | GET Method | POST Method |
| Data Transmission | Sends data appended to the URL | Sends data in the request body |
| Data Visibility | Visible in the URL | Not visible, more secure |
| Use Case | Suitable for retrieving data | Suitable for submitting data, like form inputs |
| Idempotence | Safe and idempotent | Not idempotent, may result in duplicate actions if repeated |
A more advanced user-experience-related issue is the decrease in websites’ loading time. The following are some of the strategies one can apply:
Varieties of CSS techniques can be applied in centering an element both vertically and horizontally.
To style a whole web page at a go, an external CSS stylesheet is generally used. This links the stylesheet to the HTML document. within the <head> section using the <link> tag. In the file styles.css, global styles can be defined to apply to all elements on the page.
SVG (Scalable Vector Graphics) is an XML-based format for creating vector images. We see other raster image formats like PNG or JPEG that are scalable but they might lose overall quality. In SVG, we see they do not lose any quality, irrespective of browsers, devices or size used in the website. Therefore primarily, SVG is used for icons, logos, illustrations and other graphics. SVG’s hard-coded embeddings and properties can be easily read by HTML and do not lose quality on scaling. It also supports interactivity and animation, making it versatile for web use.
| Aspect | Static Web Pages | Dynamic Web Pages |
| Content | Fixed content, does not change | Content is generated dynamically, often from a database |
| Technology | Simple HTML/CSS | Requires server-side scripting like PHP, ASP.NET |
| Interactivity | Limited, mainly for displaying information | Highly interactive, tailored content for users |
| Performance | Faster load times, fewer server resources | Slower due to server processing |
HTML <canvas> elements can draw graphics on any web page through JavaScript. Any web developer using it can create 2D shapes, and images, along with animations. Hence, it is commonly used in creating dynamic graphics like charts, visual effects and game interfaces.
Here’s a basic example:
There are three main types of CSS, each used for different purposes:
<p style=”color: blue;”>This is a blue paragraph.</p>
<style>
p {
color: blue;
}
</style>
<link rel=”stylesheet” href=”styles.css”>
| Aspect | WebSockets | HTTP Polling |
| Communication | Full-duplex, continuous connection | Client regularly requests updates |
| Efficiency | More efficient, reduces unnecessary data transfer | Less efficient, can cause server load |
| Use Case | Real-time applications like chat, gaming | Applications with less frequent updates |
| Latency | Low latency, real-time data exchange | Higher latency due to repeated requests |
AJAX (Asynchronous JavaScript and XML) is a technique used to create dynamic, interactive web applications. We often use it to update content asynchronously, exchanging all the data with a server in the background. It also does not reload the entire page while in use. AJAX is frequently used for form submissions, loading data, updating parts of a dynamic page, etc. Here’s a simple example:
| Aspect | Single-Page Application (SPA) | Multi-Page Application (MPA) |
| Navigation | Updates content dynamically without refreshing the page | Requires full page reloads for navigation |
| Performance | Faster after initial load, less data transfer | Slower as each page load requires a new request |
| Development | Complex, requires JavaScript frameworks like React, Angular | Simpler, traditional approach using HTML/CSS/JS |
| SEO | More challenging, requires additional SEO techniques | Easier to implement SEO |
We use lazy loading to defer the loading time of non-critical resources like images, videos or scripts. These resources do not require to be loaded in the very initial phase of website loading, as images and videos can be loaded after some milliseconds from page reload or when the user scrolls down to that resource. Therefore, we see all the important texts, colours, sliders, carousels, navbar, etc. are loaded first, ignoring bigger-sized images or videos which could have taken enough time to load.
| Aspect | HTTP 1.1 | HTTP 2.0 |
| Multiplexing | One request per connection | Multiple requests on a single connection |
| Header Compression | No header compression | Uses HPACK for header compression |
| Server Push | Not supported | Allows server to push resources to client before requested |
| Binary Protocol | Text-based | Binary format, more efficient |
Pagination is a technique used to divide a large set of data or content into smaller, more manageable chunks or pages. It is commonly used in search results, product listings, and other data-heavy applications. Pagination improves usability by preventing the need to load all data at once, which can slow down the website and overwhelm the user.
HTML5 introduced several new APIs to enhance web development:
Popular Integrated Development Environments (IDEs) for web development include:
| Aspect | CSS Grid | Bootstrap Grid |
| Flexibility | Native CSS, highly flexible | Predefined grid system |
| Learning Curve | Steeper, more control over the layout | Easier, but less flexible |
| Use Case | Complex, custom layouts | Standard, responsive layouts |
| Browser Support | Supported by modern browsers | Requires Bootstrap library |
When we see the variable and function declarations to be moved towards the top of their containing scope refers to the Hosting in JavaScript during the program compilation. Hence, it means you can use variables and functions before they can be declared in the code.
Example:
In the above code, the declaration var hoistedVar; is hoisted, but its assignment occurs where it is written, hence undefined is logged.
Closures can allow us to retain access to the lexical scope of a function, i.e. the initial environment in which it is created even after the outer function returns any value. Mostly used for creating private variables and functions.
Example:
In this example, innerFunction forms a closure that keeps access to the count variable even after outerFunction has finished execution.
| Aspect | PNG | SVG |
| Format | Raster image format | Vector image format |
| Resolution | Fixed resolution, loses quality on scaling | Scalable without losing quality |
| Use Case | Best for detailed images, photos | Best for logos, icons, simple graphics |
| File Size | Larger file size | Typically smaller for simple graphics |
Whenever there is the need to perform non-blocking input-output operations by offloading operations to the system kernel whenever possible, we would use the event loop in Node.js. Therefore, the event loop continuously monitors the call stack to check if there is any function that needs to be executed. Overall it maintains asynchronous code in any application.
Overall, the grid system is a responsive layout scheme that allows developers to generate complex layouts using rows and columns. The grid in Bootstrap can be adjusted to different screen sizes using predefined classes for various breakpoints. The grid is based on a 12-column system, and it adapts to different screen sizes using predefined classes for various breakpoints.
Example:
In this example, two columns are created, each taking up 6 out of 12 columns, resulting in a 50/50 split. The layout is responsive, adapting to different screen sizes based on the col-md-* class.
| Aspect | Local Storage | Cookies |
| Storage Capacity | Up to 5MB per domain | Limited to 4KB per cookie |
| Expiration | Data persists until explicitly deleted | Can be set to expire automatically |
| Access | Accessible only via JavaScript | Accessible by both server and client |
| Data Storage | Stores data in key-value pairs | Stores small data like session tokens |
Pseudo-classes in CSS are used to define the special states of an element. They allow you to style elements based on their state or position in the document tree. Common examples include:
The World Wide Web Consortium (W3C) is an international organisation that develops open standards to ensure the long-term growth of the web. Founded by Tim Berners-Lee, the W3C creates standards like HTML, CSS, and XML to promote interoperability and accessibility on the web, ensuring that websites and web applications work consistently across different browsers and devices.
Grouping in CSS3 is used to apply the same style rules to multiple selectors, reducing the amount of code and making it easier to maintain. This is done by separating selectors with a comma.
Example:
In this example, the styles are applied to all <h1>, <h2>, and <h3> elements.
In JavaScript, the submit() method is used to submit a form programmatically. It can be called on a form element to trigger the form submission.
Example:
| Aspect | Local Storage | Session Storage |
| Persistence | Data persists until explicitly deleted | Data is cleared when the session ends |
| Scope | Available across all tabs and windows of the same origin | Available only within the same tab or window |
| Storage Capacity | Up to 5MB per domain | Similar to Local Storage, but scoped to the session |
| Use Case | Ideal for storing long-term data | Ideal for storing temporary data |
The ‘each()’ function in jQuery is used to iterate over a collection of elements or an array. It allows you to perform actions on each element within the collection.
Example:
In this example, all <p> elements are selected and their text color is changed to blue.
There are two main types of CDNs (Content Delivery Networks) supported in jQuery:
| Aspect | Cookies | Tokens |
| Storage | Stored in the browser, sent with every HTTP request | Stored on the client side, often in localStorage or sessionStorage |
| Security | Vulnerable to CSRF attacks | More secure, often used with JWT (JSON Web Tokens) |
| Use Case | Session management, user tracking | API authentication, secure data exchange |
| Size | Limited in size (4KB max) | Can be larger, more flexible |
| Aspect | RESTful APIs | GraphQL APIs |
| Endpoint Structure | Multiple endpoints for different resources | Single endpoint for all queries |
| Data Retrieval | Predefined structure, returns full objects | Client-defined structure, returns exactly what is requested |
| Over-fetching/Under-fetching | May result in over-fetching or under-fetching data | No over-fetching, retrieves only requested data |
| Versioning | Often requires versioning | Typically no versioning needed |
I worked on a complex e-commerce site with frequent crashes due to high traffic. I optimised the backend by implementing load balancing and caching, which resolved the performance issues.
I had to learn React for a project with a tight deadline. I managed by dedicating extra hours to study tutorials and practice coding exercises, quickly grasping the basics and applying them effectively.
Here you can say, you had collaborated with a designer who preferred a more visual approach, while you focused on code. You both agreed on regular meetings and clear documentation to align our work, which led to a successful project.
I prioritise tasks based on urgency and impact, breaking them into smaller tasks and tackling high-priority items first. I also communicate with stakeholders to manage expectations.
I discovered a hidden bug during a routine code review. I used debugging tools to trace the issue to a misconfigured variable and fixed it before it reached production.
I write unit tests and use automated testing tools to catch errors. For debugging, I use console logs and browser developer tools to identify and fix issues before deploying the code.
I refactored a legacy codebase that was difficult to maintain. I modularized the code, improved readability, and removed redundant functions, resulting in more maintainable and efficient code.
I optimised a slow website by compressing images, minifying CSS/JS files, and enabling browser caching. These steps reduced load times and improved the user experience significantly.
I integrated a payment gateway API into an e-commerce site. The challenge was handling different error responses. I resolved it by implementing thorough error handling and testing to ensure a smooth user experience.
I view critical feedback as an opportunity to improve. I listen carefully, ask questions for clarification, and make necessary adjustments to my work to meet expectations.
In conclusion, web developer interview questions help anyone preparing for web development, providing a solid understanding in both technical and non-technical aspects. Moreover, reading daily blogs regarding web development, research papers, etc, will keep you up-to-date.
In this guide, we covered different aspects of web development, like essential topics, from basic HTML and CSS questions to more advanced concepts like RESTful APIs and JavaScript practices. You can frequently make demo projects and interfaces so that you can have a good amount of practice before your web developer interview. In the end, you can have the right preparation for the interview by understanding all the questions mentioned in this blog.
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Prashant Kumar Dey
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