User Guide

isNaN() 183

isNaN()

Availability

Flash Player 5.

Usage

isNaN(expression:Object) : Boolean

Parameters

expression

A Boolean, variable, or other expression to be evaluated.

Returns

A Boolean value.

Description

Function; evaluates the parameter and returns true if the value is NaN (not a number). This

function is useful for checking whether a mathematical expression evaluates successfully to a

number.

Example

The following code illustrates return values for the isNaN() function:

trace( isNaN("Tree") );

// returns true

trace( isNaN(56) );

// returns false

trace( isNaN(Number.POSITIVE_INFINITY) )

// returns false

The following example shows how you can use isNAN() to check whether a mathematical

expression contains an error:

var dividend:Number;

var divisor:Number;

divisor = 1;

trace( isNaN(dividend/divisor) );

// output: true

// The output is true because the variable dividend is undefined.

// Do not use isNAN() to check for division by 0 because it will return false.

// A positive number divided by 0 equals Infinity (Number.POSITIVE_INFINITY).

// A negative number divided by 0 equals -Infinity (Number.NEGATIVE_INFINITY).