# Special Types

The three special types are the untyped specifier (*), Expressions that read from untyped properties are considered untyped expressions. Use of untyped expressions or properties is recommended in the following circumstances:

- When you want to defer type checking to runtime. You can use an untyped property or expression to circumvent compile-time type checking in strict mode. Note, however, that runtime type checking of assignment statements occurs whether you use strict mode or not.
- When you want to store the value `undefined` in a property. Unlike previous versions of ActionScript, the value `undefined` is not a member of the Object data type. You must use an untyped property to store the value `undefined`.

Related API Elements

Object

void | Special Type |

Usage
`functionName():void {}`

Language Version: | ActionScript 3.0

Runtime Versions: | Flash Player 9

Specifies that a function cannot return any value. The `void` type is a special type that contains exactly one value: `undefined`. It is special in that its use is limited to the return type of a function. You cannot use `void` as a type annotation for a property.

Related API Elements

undefined

Null | Special Type |

Language Version: | ActionScript 3.0

Runtime Versions: | Flash Player 9

A special data type that represents the lack of a value. The `Null` data type includes only one value: `null`. The `Null` data type is special in that it is not associated with a class. This means that you cannot use the `Null` data type as a type annotation for a property.

Related API Elements

null

© 2015 Adobe Systems Incorporated. All rights reserved.
Mon Apr 10 2017, 01:43 PM -07:00