Javascript [Electronic resources] : The Definitive Guide (4th Edition) نسخه متنی

2.8 Reserved Words

There
are a number of reserved words in JavaScript. These are
words that you cannot use as identifiers (variable names, function
names, and loop labels) in your JavaScript programs. Table 2-1 lists the keywords standardized by ECMAScript
v3. These words have special meaning to JavaScript -- they are
part of the language syntax itself.

Table 2-1. Reserved JavaScript keywords

Table 2-2 lists other reserved keywords. These
words are not currently used in JavaScript, but they are reserved by
ECMAScript v3 as possible future extensions to the language.

Table 2-2. Words reserved for ECMA extensions

In addition to some of the formally reserved words just listed,
current drafts of the ECMAScript v4 standard are contemplating the use
of the keywords as, is,
namespace, and use. Current
JavaScript interpreters will not prevent you from using these four
words as identifiers, but you should avoid them anyway.

You should also avoid using as identifiers the names of

global variables and
functions that are predefined by JavaScript. If you create variables
or functions with these names, either you will get an error (if the
property is read-only) or you will redefine the existing variable or
function -- something you should not do unless you know exactly
what you're doing. Table 2-3 lists global
variables and functions defined by the
ECMAScript v3
standard. Specific implementations may define other

global properties, and each
specific JavaScript embedding (client-side, server-side, etc.) will
have its own extensive list of global properties.[2]

Table 2-3. Other identifiers to avoid