Default values in AS3

ActionScript 3
Data type                    default value

int                                         0

uint                                       0

Number                               NaN

Boolean                                false

String                                   null

Object                                   null

All other types/classes     null

untyped or *                        undefined

dictionary[keyObj]                   undefined

The default value for a key in a Dictionary object is undefined, before the key value was assigned or after the key in the dictionary is deleted and even _before_ the key object in the dictionary was created. Flash Player won’t throw out a runtime error, instead, it returns undefined, since Dictionary defines a dynamic collection of properties.


Adobe says “TBD” for “Constant and variable declarations” in their Flex SDK Coding Conventions and Best Practices. I normally assign a default value when declaring a variable/constant of a primitive data type.

Here and Here.

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