AJAX - The Complete Reference

566 Part IV: Appendixes

As shown by the examples, special characters can be used in identifiers, particularly _

and $. These are supposed to be reserved for special purposes, such as language

implementation environments, but the reality is that they have been co-opted by JavaScript

practitioners. For example, $() is often a user-defined function that wraps document

.getElementById() in a useful way.

Reserved Words

There are numerous reserved words in JavaScript versions. Generally speaking, reserved

words are reserved from use because they already have a defined meaning in some variant

of JavaScript or a related technology. Reserved words generally are categorized in three

types:

1. Language keywords


2. Future reserved words


3. Words such as object names or related technology keywords

Table A-10 lists the words in the first two categories based upon the JavaScript 1.5

specification combined with Microsoft’s Jscript documentation.

NNOT EOTE Some reserved words related to types not found in JavaScript, like “byte,” are reserved in

some versions of ECMAScript and not others.

abstract else instanceof switch

boolean enum int synchronized

break export interface this

byte extends long throw

case false native throws

catch final new transient

char finally null true

class float package try

const for private typeof

continue function protected val

debugger goto public var

default if return void

delete implements short volatile

do import static while

double in super with

TABLE A-10 Reserved Words in JavaScript 1.5