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 let is global const can be changed

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 Same Arrow functions are slower Arrow functions have their own this

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 Rest operator Multiplication Spreads function arguments

Question 5

What is destructuring assignment?

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

Question 6

What are promises in JavaScript?

Objects representing eventual completion/async operation Callbacks only Events Functions

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()?

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

Question 9

What is the event loop in JavaScript?

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

Question 10

What are closures?

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

Question 11

What is the this keyword?

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

Question 12

What is prototypal inheritance?

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

Question 13

What are modules in JavaScript (ES6)?

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

Question 14

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

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

Question 15

What is the purpose of the fetch API?

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

Question 16

What is localStorage?

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

Question 17

What is debouncing in JavaScript?

Limit rate of function calls Remove debugs Delay execution Cancel event

Question 18

What is the difference between null and undefined?

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

Question 19

What is the "use strict" directive?

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

Question 20

What is hoisting?

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