Quizzes – EduHub

Question 1

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

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

Question 2

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

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

Question 3

What is template literals in ES6?

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

Question 4

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

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

Question 5

What is destructuring assignment?

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

Question 6

What are promises in JavaScript?

Functions Callbacks only Objects representing eventual completion/async operation Events

Question 7

What is async/await?

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

Question 8

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

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

Question 9

What is the event loop in JavaScript?

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

Question 10

What are closures?

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

Question 11

What is the this keyword?

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

Question 12

What is prototypal inheritance?

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

Question 13

What are modules in JavaScript (ES6)?

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

Question 14

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

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

Question 15

What is the purpose of the fetch API?

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

Question 16

What is localStorage?

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

Question 17

What is debouncing in JavaScript?

Limit rate of function calls Cancel event Remove debugs Delay execution

Question 18

What is the difference between null and undefined?

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

Question 19

What is the "use strict" directive?

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

Question 20

What is hoisting?

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