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.

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