• Division by 0 results in NaN only if the divisor is also 0. If the divisor is greater than 0, division by 0 results in Infinity. If the divisor is less than 0, division by 0 results in -Infinity;
• Square root of a negative number;
• The arcsine of a number outside the valid range of 0 to 1;
• Infinity subtracted from Infinity;
• Infinity or -Infinity divided by Infinity or -Infinity;
• Infinity or -Infinity multiplied by 0;

The NaN value is not a member of the int or uint data types.

The NaN value is not considered equal to any other value, including NaN, which makes it impossible to test whether an expression is NaN using the equality operator. To determine whether a number is NaN, use isNaN().

• var foo;
• var bar:*;

The value undefined also applies to uninitialized or undefined properties of dynamic objects. For example, if an object is an instance of the Object class, the value of any dynamically added property is undefined until a value is assigned to that property.

Results vary when undefined is used with various functions:

• The value returned by String(undefined) is "undefined" (undefined is converted to a string).
• The value returned by Number(undefined) is NaN.
• The value returned by int(undefined) and uint(undefined) is 0.
• The value returned by Object(undefined) is a new Object instance.
• When the value undefined is assigned to a typed variable, the value is converted to the default value of the data type.

The value undefined should not be confused with the special value null. When null and undefined are compared with the equality (==) operator, they compare as equal. However, when null and undefined are compared with the strict equality (===) operator, they compare as not equal.

// trace value of untyped and uninitialized variable
var myVar;
trace(myVar);           // Output: undefined

dynamic class A {}
var obj:A = new A()

// trace undefined property of obj
trace(obj.propName); // Output: undefined

public function Array(... args):Array

• Calling Array() with no arguments returns an empty array.
• Calling Array() with a single integer argument returns an array of the specified length, but whose elements have undefined values.
• Calling Array() with a list of specific values returns an array with elements containing each of the specified values.

Use the as operator for explicit type conversion, or type casting, when the argument is not a primitive value. For more information, see the Example section of this entry.

var obj:Object = [ "a", "b", "c" ];
      
var newArray:Array = Array( obj );

trace(newArray == obj);    // Output: false
trace(newArray[0] == obj); // Output: true
trace(newArray[0][0])      // Output: a
trace(newArray[0][1])      // Output: b
trace(newArray[0][2])      // Output: c

var obj:Object = [ "a", "b", "c" ];
      
var newArray:Array = obj as Array;

trace(newArray == obj); // Output: true
trace(newArray[0]);     // Output: a
trace(newArray[1]);     // Output: b
trace(newArray[2]);     // Output: c

public function Boolean(expression:Object):Boolean

The return value depends on the data type and value of the argument, as described in the following table:

Unlike previous versions of ActionScript, this function returns the same results as does the Boolean class constructor.

public function decodeURI(uri:String):String

The following table shows the set of escape sequences that are not decoded to characters by the decodeURI function. Use decodeURIComponent() to decode the escape sequences in this table.

package {
    import flash.display.Sprite;

    public class DecodeURIExample extends Sprite {
        public function DecodeURIExample() {
            var uri:String = "http://www.example.com/application.jsp?user=<user name='some user'></user>";
            var encoded:String = encodeURI(uri);
            var decoded:String = decodeURI(encoded);
            trace(uri);        // http://www.example.com/application.jsp?user=<user name='some user'></user>
            trace(encoded);    // http://www.example.com/application.jsp?user=%3Cuser%20name='some%20user'%3E%3C/user%3E
            trace(decoded);    // http://www.example.com/application.jsp?user=<user name='some user'></user>
        }
    }
}

public function decodeURIComponent(uri:String):String

This function differs from the decodeURI() function in that it is intended for use only with a part of a URI string, called a URI component. A URI component is any text that appears between special characters called component separators ( ":", "/", ";" and "?" ). Common examples of a URI component are "http" and "www.adobe.com".

Another important difference between this function and decodeURI() is that because this function assumes that it is processing a URI component it treats the escape sequences that represent special separator characters (; / ? : @ & = + $ , #) as regular text that should be decoded.

public function encodeURI(uri:String):String

The following table shows the entire set of basic characters that are not converted to UTF-8 escape sequences by the encodeURI function.

package {
    import flash.display.Sprite;

    public class EncodeURIExample extends Sprite {
        public function EncodeURIExample() {
            var uri:String = "http://www.example.com/application.jsp?user=<user name='some user'></user>";
            var encoded:String = encodeURI(uri);
            var decoded:String = decodeURI(encoded);
            trace(uri);        // http://www.example.com/application.jsp?user=<user name='some user'></user>
            trace(encoded);    // http://www.example.com/application.jsp?user=%3Cuser%20name='some%20user'%3E%3C/user%3E
            trace(decoded);    // http://www.example.com/application.jsp?user=<user name='some user'></user>
        }
    }
}

public function encodeURIComponent(uri:String):String

This function differs from the encodeURI() function in that it is intended for use only with a part of a URI string, called a URI component. A URI component is any text that appears between special characters called component separators ( ":", "/", ";" and "?" ). Common examples of a URI component are "http" and "www.adobe.com".

Another important difference between this function and encodeURI() is that because this function assumes that it is processing a URI component it treats the special separator characters (; / ? : @ & = + $ , #) as regular text that should be encoded.

The following table shows all characters that are not converted to UTF-8 escape sequences by the encodeURIComponent function.

public function escape(str:String):String

The following table shows all characters that are not converted to escape sequences by the escape() function.

public function int(value:Number):int

public function isFinite(num:Number):Boolean

public function isNaN(num:Number):Boolean

The following table describes the return value of isNaN() on various input types and values.

public function isXMLName(str:String):Boolean

public function Number(expression:Object):Number

public function Object(value:Object):Object

public function parseFloat(str:String):Number

public function parseInt(str:String, radix:uint = 0):Number

public function String(expression:Object):String

The following table shows the result of various input types:

public function trace(... arguments):void

public function uint(value:Number):uint

The following table describes the return value of uint() on various input types and values.

public function unescape(str:String):String

public function XML(expression:Object):XML

The following table describes return values for various input types.

public function XMLList(expression:Object):XMLList