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JavaScript Basics Quiz

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Question 1/15

How can you add a comment in JavaScript?

Select your answer

// This is a comment

&& This is a comment

# This is a comment

Question 2/15

What does "const" declare in JavaScript?

Select your answer

A type-checked variable.

A read-only reference to a value.

A variable whose value is synced to the cloud.

A variable that can be changed later.

Question 3/15

What method is used to add new elements to the end of an array?

Select your answer

push()

add()

insert()

append()

Question 4/15

Which one of these is an Arrow Function syntax?

Select your answer

(x, y) => x + y

func (x, y) => x + y

function => (x, y){ x + y }

function(x, y){ return x + y; }

Question 5/15

What is the correct syntax for referring to an external JavaScript file called 'app.js'?

Select your answer

Question 6/15

Which of the following will write "Hello World!" to the console?

Select your answer

write('Hello World!');

print('Hello World!');

log('Hello World!');

console.log('Hello World!');

Question 7/15

Which method can be used to convert a JSON string into a JavaScript object?

Select your answer

JSON.toString()

JSON.convert()

JSON.parse()

JSON.stringify()

Question 8/15

Which of the following is a string method in JavaScript?

Select your answer

setTimeout()

getElementById()

toUpperCase()

parseInt()

Question 9/15

What does "NaN" stand for in JavaScript?

Select your answer

Not-a-Number

Numerical-and-Null

Next-as-Number

Null-and-Nothing

Question 10/15

What is the output when you execute the following code?

console.log(typeof 42);

Select your answer

string

object

number

integer

Question 11/15

When the following code is executed, what will the value of the expression be?

3 == '3'

Select your answer

true

undefined

NaN

false

Question 12/15

What will the following code output?

var fruits = ['Apple', 'Banana', 'Mango'];
console.log(fruits[1]);

Select your answer

Apple

fruits

Mango

Banana

Question 13/15

Which of the following data types exists in JavaScript?

Select your answer

Character

Hexadecimal

String

Tuple

Question 14/15

What will the following expression return: Boolean(0);

Boolean(0);

Select your answer

true

undefined

null

false

Question 15/15

What is a typical use case for the "isNaN()" function?

Select your answer

To find the maximum number.

To append a string to a number.

To convert a value to a string.

To check if a value is not a number.

Your Results

You did not answer any questions correctly.

Your Answers

Question 1/15

😊 Your answer was correct 🙁 Your answer was incorrect

How can you add a comment in JavaScript?

Available answers

// This is a comment

&& This is a comment

# This is a comment

In JavaScript, comments start with

//

for single-line comments or

/* ... */

for multi-line comments.

Question 2/15

😊 Your answer was correct 🙁 Your answer was incorrect

What does "const" declare in JavaScript?

Available answers

A type-checked variable.

A read-only reference to a value.

A variable whose value is synced to the cloud.

A variable that can be changed later.

const

declares a variable that is read-only after initialization, meaning it cannot be reassigned.

Question 3/15

😊 Your answer was correct 🙁 Your answer was incorrect

What method is used to add new elements to the end of an array?

Available answers

push()

add()

insert()

append()

The

push()

method adds one or more elements to the end of an array.

Question 4/15

😊 Your answer was correct 🙁 Your answer was incorrect

Which one of these is an Arrow Function syntax?

Available answers

(x, y) => x + y

func (x, y) => x + y

function => (x, y){ x + y }

function(x, y){ return x + y; }

An Arrow Function does not use the

function

keyword and looks like

(x, y) => x + y

Question 5/15

😊 Your answer was correct 🙁 Your answer was incorrect

What is the correct syntax for referring to an external JavaScript file called 'app.js'?

Available answers

To include an external JavaScript file, you use the

<script src='app.js'></script>

syntax.

Question 6/15

😊 Your answer was correct 🙁 Your answer was incorrect

Which of the following will write "Hello World!" to the console?

Available answers

write('Hello World!');

print('Hello World!');

log('Hello World!');

console.log('Hello World!');

The function

console.log()

is used to output messages to the web console in JavaScript.

Question 7/15

😊 Your answer was correct 🙁 Your answer was incorrect

Which method can be used to convert a JSON string into a JavaScript object?

Available answers

JSON.toString()

JSON.convert()

JSON.parse()

JSON.stringify()

The

JSON.parse()

method is used to convert a JSON string into a JavaScript object.

Question 8/15

😊 Your answer was correct 🙁 Your answer was incorrect

Which of the following is a string method in JavaScript?

Available answers

setTimeout()

getElementById()

toUpperCase()

parseInt()

The

toUpperCase()

method converts a string to uppercase letters.

Question 9/15

😊 Your answer was correct 🙁 Your answer was incorrect

What does "NaN" stand for in JavaScript?

Available answers

Not-a-Number

Numerical-and-Null

Next-as-Number

Null-and-Nothing

NaN

stands for "Not-a-Number", indicating a value that is not a legal number.

Question 10/15

😊 Your answer was correct 🙁 Your answer was incorrect

What is the output when you execute the following code?

console.log(typeof 42);

Available answers

string

object

number

integer

The

typeof

operator returns

'number'

for numerical literals like

Question 11/15

😊 Your answer was correct 🙁 Your answer was incorrect

When the following code is executed, what will the value of the expression be?

3 == '3'

Available answers

true

undefined

NaN

false

The

==

operator checks for equality with type coercion. Hence

3 == '3'

true

Question 12/15

😊 Your answer was correct 🙁 Your answer was incorrect

What will the following code output?

var fruits = ['Apple', 'Banana', 'Mango'];
console.log(fruits[1]);

Available answers

Apple

fruits

Mango

Banana

Arrays in JavaScript are zero-indexed, so

fruits[1]

contains

'Banana'

Question 13/15

😊 Your answer was correct 🙁 Your answer was incorrect

Which of the following data types exists in JavaScript?

Available answers

Character

Hexadecimal

String

Tuple

JavaScript supports data types such as

String, Number, Boolean, Object

, but not specific types like

Character

Tuple

Question 14/15

😊 Your answer was correct 🙁 Your answer was incorrect

What will the following expression return: Boolean(0);

Boolean(0);

Available answers

true

undefined

null

false

The expression

Boolean(0)

returns

false

because

is considered a "falsy" value in JavaScript.

Question 15/15

😊 Your answer was correct 🙁 Your answer was incorrect

What is a typical use case for the "isNaN()" function?

Available answers

To find the maximum number.

To append a string to a number.

To convert a value to a string.

To check if a value is not a number.

The

isNaN()

function checks if a value is NaN (Not-a-Number).