JavaScript Online Quiz with Answers

JavaScript MCQ with Answers

1. Which keyword is used to declare a variable in JavaScript?

i). var

ii). let

iii). const

iv). All of the Above

2. What is the correct way to write a comment in JavaScript?

i). <!-- This is a comment -->

ii). // This is a comment

iii). /* This is a comment */

iv). # This is a comment

3. Which built-in method converts a string to lowercase letters?

i). toLowerCase()

ii). lowerCase()

iii). convertToLower()

iv). toLower()

4. Which of the following is not a JavaScript data type?

i). boolean

ii). string

iii). character

iv). number

5. What will the following code output?
console.log(2 + '2');

i). '22'

ii). 4

iii). 2 + '2'

iv). NaN

6. How do you create a new object in JavaScript?

i). var obj = {};

ii). var obj = new Object();

iii). Both a and b

iv). None of the above

7. What is the output of the following code?
console.log(typeof NaN);

i). number

ii). NaN

iii). undefined

iv). object

8. What does the "this" keyword refer to in JavaScript?

i). It refers to the previous object

ii). It refers to the current object

iii). It refers to the global object

iv). It refers to the parent object

9. Which function is used to parse a string to an integer in JavaScript?

i). parseInt()

ii). parseFloat()

iii). toInteger()

iv). convertToInt()

10. What is the correct way to write an if statement in JavaScript?

i). if i = 5

ii). if (i == 5)

iii). if [i = 5]

iv). if {i == 5}

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11. Which operator is used to compare both value and type in JavaScript?

i). ==

ii). ===

iii). !=

iv). !==

12. What will the following code output?
console.log(2 * '2');

i). 4

ii). '22'

iii). NaN

iv). TypeError

13. How do you add a single-line comment in JavaScript?

i). <!-- This is a comment -->

ii). // This is a comment

iii)./* This is a comment */

iv). # This is a comment

14. Which function is used to round a number to the nearest integer in JavaScript?

i). round()

ii). ceil()

iii). floor()

iv). toInteger()

15. What does the "typeof" operator return for an array?

i). object

ii). array

iii). typeof

iv). None of the

16. How do you access the length of an array in JavaScript?

i). array.size

ii). array.length

iii). array.count

iv). array.size()

17. What is the correct way to check if a variable is an array in JavaScript?

i). typeof variable === 'array'

ii). variable.isArray()

iii).Array.isArray(variable)

iv). variable instanceof Array

18. What is the result of the following code?
console.log(3 + 2 + '7');

i). 57

ii). 327

iii). 12

iv). '57'

19. How do you convert a string to a number in JavaScript?

i). toInt()

ii). convertToNumber()

iii). Number()

iv). parseNumber()

20. What will the following code output?
console.log(typeof null);

i). null

ii). undefined

iii). object

iv). typeof

21. Which function is used to remove the last element from an array in JavaScript?

i). array.pop()

ii). array.removeLast()

iii). array.slice(-1)

iv). array.splice(-1)

22. What is the output of the following code?
console.log(0.1 + 0.2 == 0.3);

i). true

ii). false

iii). NaN

iv). SyntaxError

23. Which method is used to add new elements to the end of an array in JavaScript?

i). array.push()

ii). array.append()

iii). array.add()

iv). array.concat()

24. How do you check if a variable has a value of NaN in JavaScript?

i). isNaN(variable)

ii). variable.isNaN()

iii). variable == NaN

iv). typeof variable === 'NaN'

25. What will the following code output?
console.log(typeof []);

i). object

ii). array

iii). typeof

iv). None of the above

26. Which operator is used for exponentiation in JavaScript?

i). ^

ii). **

iii). //

iv). ~

27. What does the "continue" statement do in a loop?

i). It stops the execution of the loop.

ii). It skips the current iteration of the loop and continues to the next iteration.

iii). It exits the loop completely.

iv). It restarts the loop from the beginning.

28. What is the output of the following code?
console.log(4 > 3 > 2);

i). true

ii). false

iii). NaN

iv). SyntaxError

29. Which method is used to remove the first element from an array in JavaScript?

i). array.removeFirst()

ii). array.shift()

iii). array.splice(0, 1)

iv). array.slice(1)

30. What is the correct way to define a function in JavaScript?

i). function myFunction() {}

ii). var

iii). const myFunction = function() {}

iv). const myFunction = () => {}

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