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The 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.


Boolean true or false after evaluating expression.


  • 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.


XPath 1.0 4.3

Gecko support


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