Reserved Words

Some reserved words are used by the ActionScript interpreter to denote specific built-in language features such as statements and operators. They are reserved for use by the interpreter, and we must avoid using them as identifiers in our code. Using a reserved word for a purpose other than its reserved internal purpose causes an error in most cases. The reserved words of ActionScript are listed in Table 14-1.

Table 14-1. ActionScript's Reserved Words

add*	for	lt*	tellTarget*
and*	function	ne*	this
break	ge*	new	typeof
continue	gt*	not*	var
delete	if	on	void
do	ifFrameLoaded*	onClipEvent	while
else	in	or*	with
eq*	le*	return

* Flash 4 reserved words deprecated in Flash 5.

You should also try to avoid using the keywords listed in Table 14-2. They are not part of ActionScript in Flash 5 but may become a part of the language in the future because they are slated for potential use by ECMA-262.

Table 14-2. Potential Future Reserved Words

abstract	extends	private
boolean	final	protected
byte	finally	public
case	float	short
catch	goto	static
char	implements	super
class	import	switch
const	instanceof	synchronized
debugger	int	throws
default	interface	transient
double	long	try
enum	native	volatile
export	package

In addition to the formally defined keywords, you should also avoid using the names of built-in properties, methods, and objects as identifiers in your code. Doing so overrides the default behavior of the property, method, or object in question. For example:

Date = new Object( ); // Oops! We just disabled the Date( ) constructor

Now we can no longer create Date objects:

var now = new Date( ); // Sets now to undefined trace(now); // Displays the empty string, not the current time and date