Script” is a trademark licensed from Sun Microsystems (now Oracle) used to describe
Netscape’s (now Mozilla’s) implementation of the language. Netscape submitted the
language for standardization to ECMA—the European Computer Manufacturer’s As-
sociation—and because of trademark issues, the standardized version of the language
was stuck with the awkward name “ECMAScript.” For the same trademark reasons,
Microsoft’s version of the language is formally known as “JScript.” In practice, just
only to refer to the language standard.
For the last decade, all web browsers have implemented version 3 of the ECMAScript
standard and there has really been no need to think about version numbers: the lan-
guage standard was stable and browser implementations of the language were, for the
most part, interoperable. Recently, an important new version of the language has been
defined as ECMAScript version 5 and, at the time of this writing, browsers are beginning
to implement it. This book covers all the new features of ECMAScript 5 as well as all
the long-standing features of ECMAScript 3. You’ll sometimes see these language ver-
abbreviated as JS.
When we’re speaking of the language itself, the only version numbers that are relevant
are ECMAScript versions 3 or 5. (Version 4 of ECMAScript was under development
for years, but proved to be too ambitious and was never released.) Sometimes, however,
These are Mozilla’s version numbers: version 1.5 is basically ECMAScript 3, and later
versions include nonstandard language extensions (see Chapter 11). Finally, there are
current version of the V8 engine is 3.0.
To be useful, every language must have a platform or standard library or API of func-
defines a minimal API for working with text, arrays, dates, and regular expressions but
does not include any input or output functionality. Input and output (as well as more
sophisticated features, such as networking, storage, and graphics) are the responsibility
browser in Chapter 12). Part I of this book covers the language itself and its minimal
manipulation API by looking up “Array” in this part of the book, for example.