JavaScript Variables, Data Types, and Operators Quiz

What is the output of the following code?

• 5

• 3

• 8

• 15

Answer explanation

The code likely involves a calculation that results in 8. This could be from adding two numbers, such as 5 and 3, or another operation that totals 8. Therefore, the correct answer is 8.

What will be the result of true && false?

• true

• false

• undefined

• null

Answer explanation

In a logical AND operation (&&), the result is true only if both operands are true. Since one operand is false, the overall result is false.

Which operator is used to concatenate two strings in JavaScript?

• +

• -

• *

• /

Answer explanation

In JavaScript, the '+' operator is used to concatenate two strings. For example, 'Hello' + ' World' results in 'Hello World'. The other operators (-, *, /) are used for arithmetic operations, not string concatenation.

Which statement is used to skip the current iteration in a loop?

• break

• skip

• continue

• return

Answer explanation

The 'continue' statement is used in loops to skip the current iteration and proceed to the next one. In contrast, 'break' exits the loop, 'return' exits a function, and 'skip' is not a valid statement.

What is the correct way to declare a variable in JavaScript?

• var myVariable

• let myVariable

• const myVariable

• All of the above

Answer explanation

In JavaScript, variables can be declared using 'var', 'let', or 'const'. Each keyword has its own scope and behavior, making 'All of the above' the correct choice as they are all valid ways to declare a variable.

What is the output of the above code?

• 5

• 6

• 8

• 9

Answer explanation

The code uses the exponentiation operator (**). Here, 2 ** 3 means 2 raised to the power of 3, which equals 8. Therefore, the output of the code is 8.

What is the purpose of the const keyword in JavaScript?

• To declare a variable that can be reassigned

• To declare a variable that cannot be reassigned

• To declare a function

• To declare a block of code

Answer explanation

The const keyword in JavaScript is used to declare a variable that cannot be reassigned. This means once a variable is assigned a value using const, it cannot be changed, ensuring its immutability.

What is the output of the above code?

• 15

• "105"

• "15"

• 105

Answer explanation

In JavaScript, when you use the + operator with a string and a number, the number is converted to a string. Here, '10' (string) + 5 (number) results in '10' + '5', which gives '105' (string). Thus, the output is '105'.

How do you create an array in JavaScript?

• let arr = "1, 2, 3";

• let arr = [1, 2, 3];

• let arr = (1, 2, 3);

• let arr = {1, 2, 3};

Answer explanation

In JavaScript, arrays are created using square brackets. The correct syntax is 'let arr = [1, 2, 3];'. The other options either use incorrect syntax or data types that do not define an array.

What is the output of the above code?

• true

• false

Answer explanation

The code uses the loose equality operator (==), which compares values after type coercion. Here, '10' (string) is converted to 10 (number), making x and y equal. Thus, the output is true.