What happens when you try to access a variable that has not been declared in JavaScript?

What happens when you add two numbers using the + operator in JavaScript?

A). The numbers are concatenated

B). The numbers are multiplied

C). The numbers are added

D). An error occurs

What is the result of the expression true + false in JavaScript?

A). true

B). false

C). 1

D). 0

What is the result of the expression undefined + null in JavaScript?

A). undefined

B). null

C). 0

D). Error

What is the data type of the value NaN in JavaScript?

A). Number

B). String

C). Object

D). Undefined

Which of the following is a primitive data type in JavaScript?

A). Array

B). Object

C). Function

D). String

Which of the following is a valid JavaScript symbol?

A). symbol

B). &symbol

C). #symbol

D). Symbol('description')

What is the default value of a variable in JavaScript if it is not initialized?

A). null

B). undefined

C). 0

D). 'undefined'

Which of the following is a valid way to represent the value null in JavaScript?

A). undefined

B). NULL

C). null

D). None of the above

Which of the following statements is true about primitive data types in JavaScript?

A). They have methods and properties

B). They can be used as keys in objects

C). They are instances of Object

D). They are passed by value

Which of the following statements about primitive values in JavaScript is true?

A). They are mutable

B). They are passed by reference

C). They are stored on the heap

D). They are immutable