Quizzes – EduHub

Question 1

What is the difference between let, const, and var?

const can be changed let is global All same var is function-scoped, let/const are block-scoped; const cannot be reassigned

Question 2

What are arrow functions and how do they differ from regular functions?

Same Arrow functions have no own this, no arguments, cannot be constructors Arrow functions are slower Arrow functions have their own this

Question 3

What is template literals in ES6?

JSX HTML templates String concatenation String literals using backticks with embedded expressions

Question 4

What is the spread operator (...) used for?

Multiplication Spreads function arguments Rest operator Expands arrays/objects into individual elements

Question 5

What is destructuring assignment?

Merge objects Delete properties Extract values from arrays or objects into variables Assign default values

Question 6

What are promises in JavaScript?

Objects representing eventual completion/async operation Callbacks only Events Functions

Question 7

What is async/await?

Old way Callback hell Replaces promises Syntactic sugar over promises, makes async code look synchronous

Question 8

What is the difference between map() and forEach()?

map returns a new array, forEach does not Same forEach returns array map is faster

Question 9

What is the event loop in JavaScript?

Animation loop Game loop Handles asynchronous callbacks, queues tasks Render loop

Question 10

What are closures?

Global variable Loop variable Function with access to its outer scope even after outer function returns Private variable

Question 11

What is the this keyword?

Current function Global object Parent object Refers to the object that is executing the current function

Question 12

What is prototypal inheritance?

No inheritance Class inheritance Copy properties Objects inherit properties from other objects via prototype chain

Question 13

What are modules in JavaScript (ES6)?

HTML modules Node.js only External libraries Import/export syntax to split code into files

Question 14

What is the difference between == and ===?

=== checks value and type, == converts types == is stricter Same No difference

Question 15

What is the purpose of the fetch API?

Manipulate DOM Store data Make HTTP requests and handle responses Read files

Question 16

What is localStorage?

Cookie Database Session storage Store key-value pairs persistently in browser

Question 17

What is debouncing in JavaScript?

Delay execution Limit rate of function calls Cancel event Remove debugs

Question 18

What is the difference between null and undefined?

undefined means not assigned, null is intentional absence undefined is an object Same null is undefined

Question 19

What is the "use strict" directive?

Old mode Enforces stricter parsing and error handling Disables features Debug mode

Question 20

What is hoisting?

Only functions Variable/function declarations moved to top of scope Not possible Throws error