Javascript Data Types MCQ

In JavaScript, the primitive data types are String, Boolean, Number, Null, and Undefined.
An array is not a primitive data type, but is instead an object.

While A, D, and E are all valid ways to create a new string in JavaScript,
using the "new" keyword and the String constructor function (as in C) is not recommended,
because it can cause confusion with the primitive string data type.
It is better to use either of the other options.

The typeof operator in JavaScript returns a string indicating the type of the operand. In this case, the operand is the variable num, which has been assigned the value of 10, which is a number. Therefore, the typeof operator will return "number".

While A, B, D, and E are all valid ways to create a new number in JavaScript, using the "new" keyword and the Number constructor function (as in C) is not recommended,
because it can cause confusion with the primitive number data type.
It is better to use either of the other options.

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.

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.

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.

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"

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".

The /= operator in JavaScript is an assignment operator that divides the value of the left operand by the value of the right operand and assigns the result to the left operand.
In this case, the variable num is initially assigned the value 10, which is a number.
On the second line, num is divided by 5 using the /= operator.
The result of the division is 2, which is then assigned back to num.
Therefore, num now has a value of 2, and when it is logged to the console, the value 2 will be displayed.

The toUpperCase() method in JavaScript is a string method that converts all the characters in a string to uppercase.
In this case, the toUpperCase() method is called on the string "Hello", which converts all the characters in the string to uppercase.
The result is the string "HELLO", which is logged to the console.

The Map data type in JavaScript is a constructor that creates a new map object, which is a collection of key-value pairs.
The set method is used to add a new key-value pair to the map object.
In this case, two key-value pairs are added to the map object using the set method.
The size property is used to get the number of key-value pairs in the map object.
Since there are 2 key-value pairs in the map object, the size property will return 2.

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.

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.

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.

In JavaScript, an object is a collection of key-value pairs. In this case, the object is an array, which is a special type of object that stores a list of items in a specific order.

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

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

This function takes in a single argument, str, and uses the toUpperCase() method to convert the string to uppercase.