JavaScript and Web Development

1. What is React primarily used for?

• A. Building user interfaces ✓
• B. Managing databases
• C. Styling webpages
• D. Writing server-side code

💡 React is a popular JavaScript library used for building interactive user interfaces.

2. What is a JavaScript function used to display an alert box called?

• A. alert() ✓
• B. popup()
• C. notify()
• D. message()

💡 The alert() function displays a popup alert box with a specified message.

3. What does 'npm' stand for?

• A. Node Package Manager ✓
• B. New Program Module
• C. Network Protocol Manager
• D. Node Program Method

💡 npm stands for Node Package Manager, used to install and manage JavaScript packages.

4. What does 'addEventListener' do in JavaScript?

• A. Attaches an event handler to an element ✓
• B. Deletes an element
• C. Creates a new webpage
• D. Styles an element

💡 'addEventListener' attaches a function that runs when a specified event occurs on an element.

5. What is the purpose of 'querySelector' in JavaScript?

• A. To select an HTML element based on a CSS selector ✓
• B. To create a new element
• C. To delete an element
• D. To style an element

💡 'querySelector' selects the first HTML element that matches a specified CSS selector.

6. What is the purpose of 'const' in JavaScript?

• A. To declare a variable that cannot be reassigned ✓
• B. To declare a variable that can change
• C. To create a loop
• D. To define a function

💡 'const' declares a variable whose reference cannot be reassigned after its initial value is set.

7. Which keyword declares a variable in modern JavaScript that can be reassigned?

• A. var
• B. let ✓
• C. const
• D. define

💡 'let' declares a block-scoped variable in modern JavaScript that can be reassigned later.

8. What does 'NaN' stand for in JavaScript?

• A. Not a Number ✓
• B. No Assigned Number
• C. New Array Node
• D. Null and Null

💡 'NaN' stands for 'Not a Number', representing an invalid or undefined numeric result.

9. What does 'async/await' help manage in JavaScript?

• A. Asynchronous operations ✓
• B. Loops
• C. Variable declarations
• D. CSS styling

💡 'async/await' provides a cleaner syntax for working with asynchronous operations in JavaScript.

10. What is a callback function?

• A. A function passed as an argument to another function, to be executed later ✓
• B. A function that runs immediately
• C. A type of variable
• D. A CSS property

💡 A callback function is passed as an argument to another function and executed at a later point.

11. What does '===' check for in JavaScript?

• A. Strict equality (value and type) ✓
• B. Loose equality (value only)
• C. Assignment
• D. Inequality

💡 '===' checks for strict equality, comparing both the value and the type of two operands.

12. What does 'localStorage' allow in JavaScript?

• A. Storing data in the browser that persists across sessions ✓
• B. Sending data to a server
• C. Deleting cookies
• D. Compiling JavaScript code

💡 'localStorage' allows web applications to store data in the browser that persists even after the browser is closed.

13. What does 'DOM manipulation' refer to?

• A. Changing the content or structure of a webpage using JavaScript ✓
• B. Writing CSS
• C. Creating a database
• D. Compiling code

💡 DOM manipulation involves using JavaScript to dynamically change a webpage's content or structure.

14. What does AJAX allow web pages to do?

• A. Update content without reloading the page ✓
• B. Change the CSS styling
• C. Compile the code
• D. Create a database

💡 AJAX allows web pages to update content asynchronously without needing a full page reload.

15. What is JSON commonly used for?

• A. Exchanging data between a server and a client ✓
• B. Styling webpages
• C. Structuring HTML
• D. Compiling code

💡 JSON is commonly used to exchange structured data between a server and client application.