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Home / Interview Subjects / Web Developer
WithoutBook LIVE Mock Interviews Web Developer Related interview subjects: 20

Interview Questions and Answers

Know the top Web Developer interview questions and answers for freshers and experienced candidates to prepare for job interviews.

Total 50 questions Interview Questions and Answers

The Best LIVE Mock Interview - You should go through before interview

Know the top Web Developer interview questions and answers for freshers and experienced candidates to prepare for job interviews.

Interview Questions and Answers

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Freshers / Beginner level questions & answers

Ques 1

Explain the box model in CSS.

The box model consists of content, padding, border, and margin. It defines the spacing and dimensions of an element.

Example:

div {
  width: 200px;
  padding: 20px;
  border: 2px solid black;
  margin: 10px;
}
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Ques 3

Explain the purpose of the 'box-sizing' property in CSS.

The 'box-sizing' property defines how the width and height of an element are calculated, including the padding and border, or excluding them.

Example:

div {
  box-sizing: border-box;
}
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Ques 4

What is the purpose of the 'cookie' in web development?

Cookies are small pieces of data stored on the client's machine, used to store user information and maintain state between HTTP requests.

Example:

document.cookie = 'username=John; expires=Thu, 18 Dec 2024 12:00:00 UTC; path=/';
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Ques 8

Explain the difference between 'localStorage' and 'sessionStorage'.

'localStorage' persists even when the browser is closed and reopened, while 'sessionStorage' data is only available for the duration of the page session.
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Ques 10

What is the role of the 'meta' tag with the 'charset' attribute in HTML?

The 'meta' tag with the 'charset' attribute specifies the character encoding for the HTML document, ensuring proper text rendering.

Example:

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Ques 11

What is the 'event.preventDefault()' method in JavaScript used for?

'event.preventDefault()' is used to prevent the default behavior associated with an event, such as preventing a form submission or a link from navigating.

Example:

document.getElementById('myForm').addEventListener('submit', function(event) {
  event.preventDefault();
  // additional handling code
});
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Intermediate / 1 to 5 years experienced level questions & answers

Ques 14

Differentiate between sessionStorage and localStorage in HTML5.

sessionStorage stores data for the duration of a page session, while localStorage stores data with no expiration time.

Example:

sessionStorage.setItem('key', 'value');
localStorage.setItem('key', 'value');
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Ques 15

How does CSS specificity work?

Specificity determines which CSS rule takes precedence when multiple conflicting rules target the same element.

Example:

div#myId {
  color: blue;
}
#myId {
  color: red;
}
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Ques 16

What is responsive web design?

Responsive web design ensures that web applications render well on various devices and window or screen sizes.

Example:

@media screen and (max-width: 600px) {
  body {
    background-color: lightblue;
  }
}
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Ques 17

What is the purpose of the 'this' keyword in JavaScript?

The 'this' keyword refers to the current execution context and allows access to properties and methods of the current object.

Example:

const person = {
  name: 'John',
  greet: function() {
    console.log('Hello, ' + this.name + '!');
  }
};
person.greet();
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Ques 18

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

CORS is a security feature implemented by web browsers to restrict web pages from making requests to a different domain than the one that served the web page.
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Ques 19

What is the purpose of the 'async' and 'await' keywords in JavaScript?

The 'async' keyword is used to declare an asynchronous function, and 'await' is used to pause the execution of the function until the Promise is settled.

Example:

async function fetchData() {
  let response = await fetch('https://api.example.com/data');
  let data = await response.json();
  console.log(data);
}
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Ques 20

How does the 'localStorage' differ from 'sessionStorage' in HTML5?

'localStorage' persists even when the browser is closed and reopened, while 'sessionStorage' data is only available for the duration of the page session.
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Ques 21

What is the significance of the 'viewport' meta tag in HTML?

The 'viewport' meta tag controls the layout and scaling of the webpage on mobile devices, ensuring proper rendering on various screen sizes.

Example:

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Ques 24

Explain the concept of 'hoisting' in JavaScript.

Hoisting is a JavaScript behavior where variable and function declarations are moved to the top of their containing scope during the compilation phase.

Example:

console.log(x); // undefined
var x = 5;
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Ques 25

Explain the 'same-origin policy' in the context of web security.

The 'same-origin policy' is a security measure that restricts web pages from making requests to a different domain than the one that served the web page.
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Ques 27

Explain the concept of 'Promises' in JavaScript.

Promises are objects representing the eventual completion or failure of an asynchronous operation, allowing better handling of asynchronous code.

Example:

const fetchData = new Promise((resolve, reject) => {
  // asynchronous code
});
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Ques 29

What is the purpose of the 'async' attribute in a script tag?

The 'async' attribute in a script tag allows the script to be downloaded asynchronously, without blocking the HTML parsing, and then executed.

Example:

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Ques 30

What is the purpose of the 'role' attribute in HTML?

The 'role' attribute is used to define the purpose or type of an element for accessibility, helping assistive technologies interpret content.

Example:

Unchecked
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Ques 31

What is the purpose of the 'fetch' API in JavaScript?

The 'fetch' API is used to make HTTP requests and handle responses in a more flexible and modern way compared to the traditional 'XMLHttpRequest'.

Example:

fetch('https://api.example.com/data')
  .then(response => response.json())
  .then(data => console.log(data));
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Ques 32

What is the purpose of the 'transition' property in CSS?

The 'transition' property is used to create smooth transitions between different property values, allowing for animation effects.

Example:

div {
  transition: width 2s, height 2s;
}
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Ques 33

Explain the purpose of the 'transform' property in CSS.

The 'transform' property is used to apply 2D or 3D transformations to elements, such as scaling, rotating, and translating.

Example:

div {
  transform: rotate(45deg);
}
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Ques 34

Explain the concept of 'Progressive Enhancement' in web development.

Progressive Enhancement is a strategy where the core functionality and content are delivered to all users, with enhanced features provided to those with modern browsers or devices.
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Ques 35

What is the purpose of the 'aria-*' attributes in HTML?

The 'aria-*' attributes are used to enhance the accessibility of web content by providing additional information to assistive technologies.

Example:

X
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Ques 36

How does 'localStorage' differ from 'cookies' in web development?

'localStorage' allows for larger data storage on the client side, while cookies have size limitations and are sent with every HTTP request.
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Ques 37

What is the purpose of the 'V8' engine in the context of JavaScript?

The 'V8' engine is an open-source JavaScript engine developed by Google, used in Chrome and Node.js, responsible for executing JavaScript code in the browser or server environment.
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Ques 38

Explain the concept of 'Immutable Data' in JavaScript.

Immutable data cannot be changed once created, promoting safer state management and reducing bugs in applications.

Example:

const array = [1, 2, 3];
const newArray = [...array, 4];
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Ques 39

Explain the purpose of the 'SQL JOIN' operation in database queries.

The 'SQL JOIN' operation combines rows from two or more tables based on a related column, allowing the retrieval of data from multiple tables in a single query.

Example:

SELECT users.username, orders.order_id FROM users
JOIN orders ON users.user_id = orders.user_id;
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Ques 40

What is the purpose of the 'transition' property in CSS?

The 'transition' property is used to create smooth transitions between different property values, allowing for animation effects.

Example:

div {
  transition: width 2s, height 2s;
}
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Experienced / Expert level questions & answers

Ques 41

Explain the concept of closures in JavaScript.

Closures allow a function to access variables from its outer scope even after the function has finished executing.

Example:

function outer() {
  let x = 10;
  function inner() {
    console.log(x);
  }
  return inner;
}
const closureExample = outer();
closureExample();
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Ques 42

What is AJAX, and how does it work?

AJAX (Asynchronous JavaScript and XML) allows web pages to be updated asynchronously by exchanging small amounts of data with the server behind the scenes.

Example:

var xhr = new XMLHttpRequest();
xhr.open('GET', 'https://api.example.com/data', true);
xhr.onreadystatechange = function() {
  if (xhr.readyState == 4 && xhr.status == 200) {
    console.log(xhr.responseText);
  }
};
xhr.send();
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Ques 43

Explain the concept of event delegation in JavaScript.

Event delegation involves using a single event listener to manage all related events for a specific type, reducing the number of event listeners.

Example:

document.getElementById('parentElement').addEventListener('click', function(event) {
  if (event.target.tagName === 'BUTTON') {
    console.log('Button clicked!');
  }
});
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Ques 44

How can you optimize the performance of a website?

Performance optimization techniques include minimizing HTTP requests, using asynchronous loading, optimizing images, and employing caching strategies.
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Ques 46

Explain the concept of 'WebSockets' and how they differ from HTTP.

WebSockets provide a full-duplex communication channel over a single, long-lived connection, enabling real-time communication between the client and server, unlike the request-response nature of HTTP.
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Ques 47

Explain the concept of 'Cross-site Scripting (XSS)' and how to prevent it.

XSS is a security vulnerability where attackers inject malicious scripts into web pages. To prevent it, developers should sanitize user input, use proper encoding, and implement Content Security Policy (CSP).
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Ques 48

What is the purpose of the 'SQL Injection' attack and how can it be prevented?

SQL Injection is an attack where malicious SQL statements are inserted into user inputs, leading to unauthorized access or data manipulation. Prevention involves using parameterized queries and input validation.
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Ques 49

Explain the concept of 'Cross-Origin Embedder Policy' (COEP) in web security.

COEP is a security policy that controls whether a document can be embedded in another document across different origins, enhancing security by preventing unauthorized embedding.
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Ques 50

Explain the concept of 'Debouncing' in JavaScript.

Debouncing is a technique used to ensure that time-consuming tasks do not fire so often, making it more efficient for tasks like handling input events.

Example:

function debounce(func, delay) {
  let timeoutId;
  return function() {
    clearTimeout(timeoutId);
    timeoutId = setTimeout(() => func.apply(this, arguments), delay);
  };
}
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