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

Question 3

What is template literals in ES6?

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

Question 4

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

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

Question 5

What is destructuring assignment?

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

Question 6

What are promises in JavaScript?

Events Callbacks only Objects representing eventual completion/async operation Functions

Question 7

What is async/await?

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

Question 8

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

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

Question 9

What is the event loop in JavaScript?

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

Question 10

What are closures?

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

Question 11

What is the this keyword?

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

Question 12

What is prototypal inheritance?

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

Question 13

What are modules in JavaScript (ES6)?

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

Question 14

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

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

Question 15

What is the purpose of the fetch API?

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

Question 16

What is localStorage?

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

Question 17

What is debouncing in JavaScript?

Cancel event Remove debugs Limit rate of function calls Delay execution

Question 18

What is the difference between null and undefined?

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

Question 19

What is the "use strict" directive?

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

Question 20

What is hoisting?

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