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These two books from the same stable are both aimed at readers that already have some basic Web and HTML experience. In case you haven't already come across it, JavaScript is primarily a high-level scripting language for client-side Web applications, although it has also begun to find server-side uses. Web developers can use JavaScript to enhance their pages; getting the users' browser to do some work in validating forms, providing interactive interfaces and other small applications. Browsers that support it include both Microsoft Internet Explorer and Netscape Navigator.

JavaScript Unleashedcontains over 800 pages of text with a 60-page index. It is one of a long line of 'Unleashed' titles, many of which have been popular reference works. Its primary author, Richard Wagner, has a strong Borland Delphi background and this shows through in places. In fact, one of the author's products, a JavaScript editor written in Delphi, is included on the book's companion CDROM.

This is a comprehensive book with chapters covering a range of themes from the current confusion in standards for Web applications - HTML 3.2 Java, JavaScript, VBScript, and ActiveX - to an exhaustive treatment of the JavaScript language, its objects and how they are manipulated.

One thing sorely lacking in the first part of the book is any real motivation. While reading the book the flowing style made is fairly easy to understand what each JavaScript feature did, but I was left wondering why I'd want to bother. One large example built up through the early chapters would have helped this reader get more from the text. The chapter on Object Orientation was particularly weak, using as it does the ubiquitous factorial function. This is not an example readily suited to object- oriented development, but is played for all its worth. Then comes the revelation; JavaScript is not really an object-oriented language.

However, this is a relatively minor complaint. More useful examples are used in the chapters on enhancing forms and using frames. Use of cookies and maintaining state is also covered. Later chapters cover server-side uses, integration with Java, error handling and debugging. All code examples are provided on the CDROM.

The JavaScript UnleashedCDROM runs under Windows 95/NT and Macintosh and contains a wealth of useful material, including a Java development kit and HTML versions of the booksTeach Yourself Java in a WeekandJava Unleashed.

At nearly£47JavaScript Unleashedis expensive, but you get a lot for your money. Recommended for anyone interested in where JavaScript fits in and how it works.

JavaScript Developer's Guideis 200 pages shorter and lacks such a comprehensive index. It is written for developers and reads much like any programming textbook. It contains a good number of example programs, some quite extensive. The cookie and frames example is especially good and there is also a complete solitaire card game written in JavaScript.

There are chapters covering the solution to real-world Web problems like authentication, database access, search engines and implementing spreadsheets. It also covers VBScript and ActiveX in some detail.

A companion CDROM contains a Java development kit, a client/server interface builder and the example source code among other goodies. Recommended for those wanting to become serious Web developers.

Such is the fast moving nature of Web technology and Java in particular that as JavaScript reference works these books are both likely to date quite quickly. If you need to keep up to date with develop-ments it might pay to take a look at the much cheaper O'Reilly effort;JavaScript -- The Definitive Guide(ISBN 1 56592 234 4,£24.50), already in its second edition.