C.1 Best Practices in Flash 6 ActionScript

	ActionScript for Flash MX: The Definitive Guide, 2nd Edition By Colin Moock
	Appendix C.  Backward Compatibility and Player Build Updates

Very little of Flash 5 ActionScript was formally deprecated in Flash 6. The following formal changes to the language were introduced in Flash 6:

• The eval( ) function cannot be used on the left side of an assignment operation.

• Function scope is defined permanently at declaration time instead of at invocation time. See Section 9.7.

The following list presents new features that are preferred over previous Flash 5 alternatives:

• Global variables should be defined on _global, not _root or Object.

• Superclass constructors should be executed via the super operator, not a manual reference to the superclass constructor function.

• All imported text should be in Unicode, not Latin 1 or Shift-JIS.

• Movie clip and button event handlers should be assigned as object properties, not with the onClipEvent(event) or on(event) syntax. See the ActionScript Language Reference for specific exceptions for individual events.

• Text field content must be accessed via the TextField.text property, not the text field's variable name.

• JPEG files should be loaded directly using loadMovie( ), not wrapped in .swf files.

• Often, timeline and onEnterFrame( ) loops can be replaced with setInterval( ).

• A local SharedObject should be used in favor of a JavaScript cookie.

• System.capabilities.version is preferred over getVersion( ) (though getVersion( ) must still be used in movies displayed in Flash Player 5).

• The Key and Mouse object events onKeyDown( ), onKeyUp( ), onMouseDown( ), and onMouseUp( ) should be used in place of analogous MovieClip events, except when updateAfterEvent( ) is required.

• The LoadVars class supercedes the loadVariables( ) function.

• Stage.scaleMode and Stage.showMenu replace fscommand("allowscale") and fscommand("showmenu").

For more best practices in Flash 6 ActionScript, see:

http://www.macromedia.com/desdev/mx/flash/whitepapers/actionscript_standards.pdf

As a rule, the new objects, classes, statements, and operators introduced in Flash 6 (as listed in the Preface) cannot be used when exporting to Flash 5 format. Three exceptions are the switch statement and the strict equality and inequality operators (= = = and !==), which are all available when exporting from the Flash MX authoring tool to Flash 5 format. When a movie is set to export as version 5, the Flash MX Output window reports any incompatibility warnings at export time.