Quizzes – EduHub

Question 1

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

All same const can be changed 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 are slower Arrow functions have no own this, no arguments, cannot be constructors Arrow functions have their own this Same

Question 3

What is template literals in ES6?

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

Question 4

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

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

Question 5

What is destructuring assignment?

Merge objects Extract values from arrays or objects into variables Delete properties 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()?

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

Question 9

What is the event loop in JavaScript?

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

Question 10

What are closures?

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

Question 11

What is the this keyword?

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

Question 12

What is prototypal inheritance?

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

Question 13

What are modules in JavaScript (ES6)?

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

Question 14

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

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

Question 15

What is the purpose of the fetch API?

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

Question 16

What is localStorage?

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

Question 17

What is debouncing in JavaScript?

Remove debugs Cancel event Delay execution Limit rate of function calls

Question 18

What is the difference between null and undefined?

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

Question 19

What is the "use strict" directive?

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

Question 20

What is hoisting?

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