Flash CS3 Documentation

ActionScript 2.0 Language Reference > ActionScript language elements > Global Functions > isNaN function

isNaN function

isNaN(expression:Object) : Boolean

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.

Availability: ActionScript 1.0; Flash Player 5

Parameters

expression:Object - A Boolean, variable, or other expression to be evaluated.

Returns

Boolean - A Boolean value.

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).

See also

NaN constant, NaN (Number.NaN property)

Flash CS3