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

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 data type of the value undefined in JavaScript?

A). String

B). Object

C). Undefined

D). Number

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

A). undefined

B). null

C). 0

D). Error

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 true == 1 in JavaScript?

A). true

B). false

C). Error

D). 1

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

A). Array

B). Object

C). Function

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 a primitive value in JavaScript?

A). A complex data structure

B). A basic data type

C). A function

D). An array

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 is a valid JavaScript symbol?

A). symbol

B). &symbol

C). #symbol

D). Symbol('description')