boolean function evaluates an expression and returns true or false.
boolean( expression )
The expression to be evaluated. The expression can refer to numbers and node-sets as well as booleans.
false after evaluating
- A number evaluates to false if it is positive or negative zero or
NaN. Otherwise, it evaluates true.
- A node-set evaluates to true if it is non-empty.
- A string evaluates to false if it an empty string. Otherwise, it evaluates to true.
- An object of a type other than the four basic types is converted to a boolean in a way that is dependent on that type.