04. Strange data types

Booleans

The boolean type variable is used in control-flow, which we will get to in the next section.

The two types it may hold are true and false.

Usually you don't declare a variable, but you rather use an expression that evaluates to a boolean value - true or false.

Null

nullsimply means nothing. It represents and evaluates to false. However, this does not mean it's empty.

var myVariable = ''; // myVariable is empty, but not null. 

Undefined

undefined means a variable that hasn't yet contained a value.

Build modern and responsive webpages

HTML & CSS

Build modern and responsive webpages Try Front-end

This book teaches HTML as if it's for anyone - hobbyists, students, and professionals - and it's full-color throughout. It utilizes information graphics and lifestyle photography to explain the topics in a simple way that is engaging. You can progress through the chapters from beginning to end or just dip into topics of particular interest at your leisure.

$ Check price
29.9929.99Amazon 4.5 logo(926+ reviews)

More Front-end resources

Aching back from coding all day?

Foam Seat Cushion

Aching back from coding all day? Try Back Problems

This foam seat cushion relieves lowerback pain, numbness and pressure sores by promoting healthy weight distribution, posture and spine alignment. Furthermore, it reduces pressure on the tailbone and hip bones while sitting. Perfect for sitting on the computer desk for long periods of time.

$ Check price
99.9599.95Amazon 4.5 logo(9,445+ reviews)

More Back Problems resources

Ad