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

Which of the following statements is true about JavaScript's null value?

A). It represents an empty string

B). It represents a non-existent value

C). It represents a boolean value

D). It represents a number

Which of the following is not a primitive value in JavaScript?

A). Number

B). Boolean

C). Object

D). String

What does the Symbol data type represent in JavaScript?

A). A unique identifier

B). A number

C). A boolean value

D). An object

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

A). Number

B). String

C). Object

D). Undefined

Which symbol is used to represent a boolean value in JavaScript?

A). #

B). $

C). !

D). true/false

Which primitive value represents absence of value or no value assigned?

A). undefined

B). null

C). 0

D). 'undefined'

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

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

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

A). null

B). undefined

C). 0

D). 'undefined'