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boolean

files/en-us/web/xml/xpath/reference/functions/boolean/index.md

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The boolean function evaluates an expression and returns true or false.

Syntax

js-nolint
boolean( expression )

Parameters

  • expression
    • : The expression to be evaluated. The expression can refer to numbers and node-sets as well as booleans.

Return value

Boolean true or false after evaluating expression.

Description

  • 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 is 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.

Specifications

XPath 1.0 4.3

Gecko support

Supported.