Quizzes – EduHub

Question 1

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

const can be changed All same let is global 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?

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

Question 3

What is template literals in ES6?

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

Question 4

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

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

Question 5

What is destructuring assignment?

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

Question 6

What are promises in JavaScript?

Functions Objects representing eventual completion/async operation Callbacks only Events

Question 7

What is async/await?

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

Question 8

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

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

Question 9

What is the event loop in JavaScript?

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

Question 10

What are closures?

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

Question 11

What is the this keyword?

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

Question 12

What is prototypal inheritance?

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

Question 13

What are modules in JavaScript (ES6)?

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

Question 14

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

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

Question 15

What is the purpose of the fetch API?

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

Question 16

What is localStorage?

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

Question 17

What is debouncing in JavaScript?

Cancel event Limit rate of function calls Delay execution Remove debugs

Question 18

What is the difference between null and undefined?

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

Question 19

What is the "use strict" directive?

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

Question 20

What is hoisting?

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