User Guide

Boolean() 129
Boolean()
Availability
Flash Player 5; behavior changed in Flash Player 7.
Usage
Boolean(expression) : Boolean
Parameters
expression
An expression to convert to a Boolean value.
Returns
A Boolean value.
Description
Function; converts the parameter expression to a Boolean value and returns a value as described
in the following list:
• If expression is a Boolean value, the return value is expression.
• If expression is a number, the return value is true if the number is not zero; otherwise the
return value is
false.
If
expression is a string, the result is true if the string has a length greater than zero; the value is
false for an empty string.
• If expression is undefined or NaN (not a number), the return value is false.
• If expression is a movie clip or an object, the return value is true.
Note: Unlike the Boolean class constructor, the Boolean() function does not use the keyword new.
Moreover, the Boolean class constructor initializes a Boolean object to false if no parameter is
specified, while the Boolean() function returns undefined if no parameter is specified.
Example
In the following example, expressions are converted from numeric to Boolean values:
trace(Boolean(-1)); // output: true
trace(Boolean(0)); // output: false
trace(Boolean(1)); // output: true
trace(Boolean(true)); // output: true
trace(Boolean(false)); // output: false
trace(Boolean("true")); // output: true
trace(Boolean("false")); // output: true
trace(Boolean("Craiggers")); // output: true
trace(Boolean("")); // output: false
This example shows a significant difference between use of the Boolean() function and the
Boolean class. The
Boolean() function creates a Boolean value, and the Boolean class creates a
Boolean object. Boolean values are compared by value, and Boolean objects are compared by
reference.
CHAPTER 5
ActionScript Core Language Elements