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

What is the result of the expression 5 + '5' in JavaScript?

A). 10

B). '55'

C). '10'

D). Error

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 true + false in JavaScript?

A). true

B). false

C). 1

D). 0

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'

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 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

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