✅ Top Javascript Interview Questions with Answers: Part-4 💻✨

31. What is a rest parameter? 
Rest parameter (...args) allows a function to accept an indefinite number of arguments as an array. 

function sum(...numbers) {
  return numbers.reduce((a, b) => a + b, 0);
}
console.log(sum(1, 2, 3)); // 6

32. What are template literals? 
Template literals use backticks (`) to embed variables and expressions. 

const name = 'Alice';
console.log(Hello, ${name}!); // Hello, Alice!

33. What is a module in JS? 
Modules help organize code into reusable files using export and import. 

// file.js
export const greet = () => console.log('Hi');

// main.js
import { greet } from './file.js';
greet();

34. Difference between default export and named export 
• Default export: One per file, imported without {}
• Named export: Multiple exports, must use the same name

// default export
export default function() {}
import myFunc from './file.js';

// named export
export const x = 5;
import { x } from './file.js';

35. How do you handle errors in JavaScript? 
Use try...catch to handle runtime errors gracefully. 

try {
  JSON.parse("invalid json");
} catch (error) {
  console.log("Caught:", error.message);
}

36. What is the use of try...catch? 
To catch exceptions and prevent the entire program from crashing. It helps with debugging and smoother user experience.

37. What is a service worker? 
A script that runs in the background of web apps. Enables features like offline access, caching, and push notifications.

38. localStorage vs. sessionStorage 
• localStorage: Data persists after tab/browser close
• sessionStorage: Data clears when the tab is closed

localStorage.setItem('user', 'John');
sessionStorage.setItem('token', 'abc123');

39. What is debounce and throttle? 
• Debounce: Waits for inactivity before running a function
• Throttle: Limits function execution to once per time interval
Used in scroll/input/resize events to reduce overhead.

40. What is the Fetch API? 
Used to make network requests. Returns a Promise. 

fetch('https://api.example.com')
  .then(res => res.json())
  .then(data => console.log(data))
  .catch(err => console.error(err));

💬 Double Tap ❤️ for Part-5!