Javascript Data Types MCQ - Quiz

Q: What is the result of the following code?

var obj = {};
console.log(Object.is(obj, {}));

A. true
B. false
C. "true"
D. "false'

Correct Option: B
Explanation:

The Object.is method in JavaScript is a method that can be used to determine whether two values are the same.
In this case, the Object.is method is called with obj and an empty object as the arguments.
Although obj and the empty object may seem similar, they are actually two distinct objects and are not the same.
Therefore, the Object.is method will return false.

Q: What is the result of the following code?

var set = new Set();
set.add(1);
set.add(2);
console.log(set.has(2));

A. true
B. false
C. "true"
D. "false"

Correct Option: A
Explanation:

The Set data type in JavaScript is a constructor that creates a new set object, which is a collection of unique values.
The add method is used to add a new value to the set object.
The has method is used to determine whether the set object includes the specified value.
In this case, two values are added to the set object using the add method.
The has method is called on the set object, with the value 2 as the argument.
Since the set object includes the value 2, the has method will return true.

Q: What is the result of the following code?

var arr = [1, 2, 3];
console.log(Array.isArray(arr));

A. true
B. false
C. "true"
D. "false"

Correct Option: A
Explanation:

The Array.isArray method in JavaScript is a method that can be used to determine whether a value is an array.
In this case, the Array.isArray method is called with the array [1, 2, 3] as the argument.
Since the value is an array, the Array.isArray method will return true.

Q: What is the result of the following code?

var num = 10;
num++;
console.log(num);

A. 10
B. 11
C. "10"
D. "11"

Correct Option: B
Explanation:

The ++ operator in JavaScript is an increment operator, which increments a number by 1.
In this case, the variable num is initially assigned the value 10, which is a number.
On the second line, num is incremented by 1 using the ++ operator.
Therefore, num now has a value of 11, and when it is logged to the console, the value 11 will be displayed.

Q: What is the result of the following code?

var num = 10;
num = "Hello";
console.log(typeof num);

A. number
B. string
C. boolean
D. undefined

Correct Option: B
Explanation:

In JavaScript, variables are dynamically-typed, which means that their type can change at runtime.
In this case, the variable num is initially assigned the value 10, which is a number.
However, on the second line, num is assigned the value "Hello", which is a string.
Therefore, the typeof operator will return "string" when it is called on num.

Q: What is the result of the following code?

var num1 = 10;
var num2 = "20";
console.log(num1 + num2);

A. 30
B. "30"
C. "1020"
D. TypeError

Correct Option: C
Explanation:

In JavaScript, the + operator can be used to add numbers or concatenate strings.
If both operands are numbers, the + operator will perform addition.
If either operand is a string, the + operator will treat both operands as strings and perform string concatenation.
In this case, the first operand (num1) is a number, but the second operand (num2) is a string.
Therefore, the + operator will treat both operands as strings and perform string concatenation, resulting in the string "1020".

Q: What is the result of the following code?

var x = true;
var y = false;
console.log(x && y);

A. true
B. false
C. "false"
D. "true"

Correct Option: B
Explanation:

The && operator in JavaScript performs a logical AND operation on its operands.
If both operands are truthy, the result is true, otherwise the result is false.
In this case, the first operand (x) is truthy (true), but the second operand (y) is falsy (false), so the result of the && operation is false.

Q: What is the result of the following code?


var str = "Hello";
var num = 10;
console.log(str + num);

A. "Hello 10"
B. "10 Hello"
C. "10"
D. "Hello10Hello"

Correct Option: A
Explanation:

In JavaScript, the + operator can be used to concatenate strings.
In this case, the + operator is used to concatenate the string "Hello" with the number 10
Since one of the operands is a string, the + operator will treat both operands as strings and perform string concatenation.
The result will be the string "Hello10"

Q: What does the following function do in JavaScript?

function greet(name) {
return "Hello, " + name + "!";
}

A. greets the user by name
B. calculates the area of a circle
C. converts a string to uppercase
D. checks if a string is a palindrome

Correct Option: A
Explanation:

This function takes in a single argument, name, and returns a greeting string that includes the name.

Q: What does the following function do in JavaScript?

function getArea(radius) {
return Math.PI * radius * radius;
}

A. calculates the area of a circle
B. converts a string to uppercase
C. checks if a string is a palindrome
D. sorts an array in ascending order

Correct Option: A
Explanation:

This function takes in a single argument, radius, and uses the Math.PI constant and the radius to calculate the area of a circle.

Javascript Data Types MCQ - Quiz

What is the result of the following code?
var obj = {}; console.log(Object.is(obj, {}));

What is the result of the following code?
var set = new Set(); set.add(1); set.add(2); console.log(set.has(2));

What is the result of the following code?
var arr = [1, 2, 3]; console.log(Array.isArray(arr));

What is the result of the following code?
var num = 10; num++; console.log(num);

What is the result of the following code?
var num = 10; num = "Hello"; console.log(typeof num);

What is the result of the following code?
var num1 = 10; var num2 = "20"; console.log(num1 + num2);

What is the result of the following code?
var x = true; var y = false; console.log(x && y);

What is the result of the following code?

What does the following function do in JavaScript?
function greet(name) { return "Hello, " + name + "!"; }

What does the following function do in JavaScript?
function getArea(radius) { return Math.PI * radius * radius; }

Javascript Data Types MCQ - Quiz

What is the result of the following code? var obj = {}; console.log(Object.is(obj, {}));

What is the result of the following code? var set = new Set(); set.add(1); set.add(2); console.log(set.has(2));

What is the result of the following code? var arr = [1, 2, 3]; console.log(Array.isArray(arr));

What is the result of the following code? var num = 10; num++; console.log(num);

What is the result of the following code? var num = 10; num = "Hello"; console.log(typeof num);

What is the result of the following code? var num1 = 10; var num2 = "20"; console.log(num1 + num2);

What is the result of the following code? var x = true; var y = false; console.log(x && y);

What is the result of the following code? var str = "Hello"; var num = 10; console.log(str + num);

What does the following function do in JavaScript? function greet(name) { return "Hello, " + name + "!"; }

What does the following function do in JavaScript? function getArea(radius) { return Math.PI * radius * radius; }

What is the result of the following code?
var obj = {}; console.log(Object.is(obj, {}));

What is the result of the following code?
var set = new Set(); set.add(1); set.add(2); console.log(set.has(2));

What is the result of the following code?
var arr = [1, 2, 3]; console.log(Array.isArray(arr));

What is the result of the following code?
var num = 10; num++; console.log(num);

What is the result of the following code?
var num = 10; num = "Hello"; console.log(typeof num);

What is the result of the following code?
var num1 = 10; var num2 = "20"; console.log(num1 + num2);

What is the result of the following code?
var x = true; var y = false; console.log(x && y);

What is the result of the following code?

What does the following function do in JavaScript?
function greet(name) { return "Hello, " + name + "!"; }

What does the following function do in JavaScript?
function getArea(radius) { return Math.PI * radius * radius; }