JavaScript Quiz

1 / 25

What is the output of console.log(5 === '5');?

false

true

undefined

NaN

2 / 25

What defines a higher-order function?

A function that must be invoked immediately.

A function that has its own scope and can't be accessed by other functions.

A function that only takes callback as an argument.

A function that can receive other functions as arguments, or return a new function.

3 / 25

What is a closure in JavaScript?

A function that can access variables from its parent scope even after the parent function has finished executing.

A type of variable that can only be used inside a function.

A method to create global variables.

A function that can only be used inside a loop

4 / 25

Which statement is used to execute a block of code repeatedly?

return

break

for

5 / 25

What will be the output of const arr = []; arr[2] = 10; console.log(arr);?

[10]

[undefined, undefined, 10]

[2, 10]

SyntaxError

6 / 25

What does console.log(new Array() instanceof Object); evaluate to?

false

undefined

true

Error

7 / 25

What is the primary mechanism that allows objects in JavaScript to inherit properties from other objects?

The super keyword

The prototype chain

The extend operator

The class keyword

8 / 25

What is a "Temporal Dead Zone" in JavaScript?

The time between the start of a function and its first line of execution.

The time it takes for a promise to resolve.

The time a variable is declared but not assigned.

he time during which let and const variables cannot be accessed after they are declared but before they are initialized.

9 / 25

What is the output of the following code? let x = 0; let output = (function(x) { delete x; return x; })(0); console.log(output);

undefined

null

Error

10 / 25

Which of the following is not a reserved word in JavaScript?

throws

short

program

interface

11 / 25

In a switch statement, what keyword terminates a case?

end

stop

break

exit

12 / 25

What is the output of console.log(myVar); var myVar = 5;?

undefined

null

ReferenceError

13 / 25

What is the correct syntax for an arrow function that returns the sum of a and b?

const add = (a, b) => a + b;

const add = a, b => a + b;

const add = function(a, b) => a + b;

function add(a, b) => a + b;

14 / 25

hat is the output of console.log(false?? 'default');?

undefined

null

false

default

15 / 25

What is the output of console.log(5 == '5');?

NaN

false

true

undefined

16 / 25

What is the correct syntax to display "Hello World" in an alert box?

alert('Hello World');

alertBox('Hello World');

displayAlert('Hello World');

msgAlert('Hello World');

17 / 25

What will console.log(this); log when executed in the global context of a browser?

this function

Window object

undefined

null

18 / 25

What will console.log(typeof null); return?

undefined

number

null

object

19 / 25

What is the output of console.log(3 + 2 + '7');?

'57'

'12'

327

20 / 25

What will console.log(NaN === NaN); evaluate to?

false

Error

undefined

true

21 / 25

Which keyword is used for a variable that can be reassigned?

static

let

readonly

const

22 / 25

Which data type in JavaScript is used to represent logical values?

Number

Undefined

Boolean

String

23 / 25

Which method is used to add a new item to the end of an array?

append()

push()

pop()

add()

24 / 25

What is the output of console.log(10 - '5');?

'5'

105

Error

25 / 25

What is the primary purpose of Promise.all()?

To return the result of the first resolved promise.

To run multiple promises sequentially

To wait until all promises are resolved or one is rejected.

To handle the first rejected promise only.

Your score is

Overview:

Think you know JavaScript? Take our JavaScript Quiz and put your coding knowledge to the test! From basics like variables and loops to advanced concepts, this quiz is perfect for learners and developers who want to level up their JS skills.