Unary operators in Javascript - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is a unary operator in JavaScript?

A unary operator is an operator that works with only one operand. It performs an operation on a single value or variable.

beginner

What does the unary plus (+) operator do?

The unary plus (+) operator converts its operand to a number if it is not already one.

beginner

How does the unary negation (-) operator work?

The unary negation (-) operator converts its operand to a number and then negates it, changing its sign.

beginner

What is the purpose of the typeof operator?

The typeof operator returns a string indicating the type of the operand, such as 'number', 'string', or 'object'.

intermediate

What does the delete operator do in JavaScript?

The delete operator removes a property from an object. It returns true if the property was successfully deleted or did not exist.

Which of the following is a unary operator in JavaScript?

A ||

B &&

C ==

D +

The plus (+) operator used alone is unary, working on one operand. The others are binary operators.

What is the result of +"5" in JavaScript?

A 5 (number)

B "5" (string)

C NaN

D undefined

The unary plus converts the string "5" to the number 5.

What does typeof null return?

A "null"

B "boolean"

C "object"

D "undefined"

typeof null returns "object" due to a historical JavaScript quirk.

What does the delete operator do?

A Deletes a property from an object

B Deletes a variable

C Deletes a function

D Deletes an array element by index

The delete operator removes a property from an object, not variables or functions.

What is the result of -true in JavaScript?

A NaN

B -1

C 1

D false

true converts to 1, then unary negation changes it to -1.

Explain what unary operators are and give three examples in JavaScript.

Think about operators that work with only one value.

Describe how the delete operator works and when you might use it.

It is not used to delete variables.