JavaScript Fundamentals

Check your understanding of JavaScript basics like variables,functions,and scope.

1. Which keyword declares a block-scoped variable that can be reassigned in JavaScript?

var let const function

2. Which of the following are considered truthy values in JavaScript (select all that apply)?

0 "false" null [] undefined

3. JavaScript is a statically typed language.

True False

4. What does 'ES' stand for in ES6 (ECMAScript 6)?

5. Which of the following is NOT a primitive data type in JavaScript?

String Number Object Boolean

6. Which array methods mutate the original array (select all that apply)?

push() map() sort() filter() splice()

7. The 'this' keyword in a global function (non-strict mode) refers to the window object in browsers.

True False

8. What operator checks both value and type equality without coercion?

9. Which of the following is fully hoisted in JavaScript?

Function declarations Function expressions Variables declared with let Variables declared with const

10. Which array methods return a new array without mutating the original (select all that apply)?

forEach() map() filter() slice() push()

11. typeof null returns 'null' in JavaScript.

True False

12. What is the result of: 3 + '3'?

13. Which data type is returned by the typeof operator for an array?

array object list collection

14. Which are primitive data types in JavaScript (select all that apply)?

Symbol Array BigInt Undefined Object

15. Variables declared with var are block-scoped.

True False

16. What method adds elements to the end of an array and returns the new length?

17. What is the value of an undeclared variable in JavaScript?

null undefined 0 Throws a ReferenceError

18. Which are valid loop structures in JavaScript (select all that apply)?

for while do-while for-each repeat-until

19. In JavaScript, objects are passed by reference.

True False

20. What keyword exits a function and returns a value?

Answered 0 of 0 — 0 correct

Company