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14.4. 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
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