A Boolean expresses a "truth" value, and can therefore be true or false. true and false are Constants, so can be used in expressions.

For example:

{ a = true }
{ b = false }
 
{ if a }
...
{ endif }
 
{ if a == true }
...
{ endif }
 
{ if a === true }
...
{ endif }

Note that in the example above, each If statement checks for the "truthfulness" of variable a, but the final statement (if a === true) also checks that a is explicitly boolean. That is because non-explicit statements perform a conversion to Boolean before making the comparison.

To explicitly convert a value to Boolean, the Boolean typecast operator - ? - should be used. Some operators, such as the boolean logic NOT operator - ! or not - also explictly convert a value to Boolean.

When converting to Boolean, the following values are considered to be false:

• A Boolean with value false
• A Number with value zero (0 or 0.0)
• An empty String - ""
• A String containing a single zero - "0"
• An empty Array (with no elements)

Every other value is considered to be true.