Web Developer Interview Questions and Answers

Ques 1. What is the difference between HTML and XHTML?

HTML is more forgiving and allows for more flexibility, while XHTML is stricter and follows XML syntax.

Example:

HTML: 
Hello World

XHTML: 
Hello World

Ques 2. What is the purpose of the 'defer' attribute in a script tag?

The 'defer' attribute delays the execution of a script until the HTML parsing is complete.

Example:

Ques 3. 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');

Ques 4. 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;
}

Ques 5. 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;
  }
}

Ques 6. 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();

Ques 7. 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.

Ques 8. 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);
}

Ques 9. 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.

Ques 10. 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:

Ques 11. What are RESTful APIs, and how do they work?

RESTful APIs (Representational State Transfer) are web APIs that adhere to the principles of REST, utilizing standard HTTP methods for communication.

Ques 12. What is the purpose of the 'defer' attribute in a script tag?

The 'defer' attribute delays the execution of a script until the HTML parsing is complete.

Example:

Ques 13. 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;

Ques 14. 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.

Ques 15. How does the 'target' attribute work in HTML forms?

The 'target' attribute specifies where to open the linked document when submitting a form, such as '_blank' to open in a new tab.

Example:

Ques 16. 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
});

Ques 17. Explain the purpose of the 'data-*' attribute in HTML.

The 'data-*' attribute is used to store custom data private to the page or application, accessible by JavaScript and CSS.

Example:

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