Quizzes – EduHub

Question 1

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

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

Question 2

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

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

Question 3

What is template literals in ES6?

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

Question 4

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

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

Question 5

What is destructuring assignment?

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

Question 6

What are promises in JavaScript?

Callbacks only Functions Objects representing eventual completion/async operation Events

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()?

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

Question 9

What is the event loop in JavaScript?

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

Question 10

What are closures?

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

Question 11

What is the this keyword?

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

Question 12

What is prototypal inheritance?

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

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 ===?

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

Question 15

What is the purpose of the fetch API?

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

Question 16

What is localStorage?

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

Question 17

What is debouncing in JavaScript?

Limit rate of function calls Delay execution Cancel event Remove debugs

Question 18

What is the difference between null and undefined?

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

Question 19

What is the "use strict" directive?

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

Question 20

What is hoisting?

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