Excerpts from the Introduction:

Before JavaScript was created, a typical web browsing experience consisted largely of displaying static pages of information. Any type of user interaction with a web page usually involved the browser sending information back to the web server where some type of server based script or other program would validate the user's data input. The server would then send back either a static error page if the user had entered invalid data or, assuming successful validation, return a static page to the web browser containing the results of the transaction. In addition, the lack of a mechanism to implement dynamic web page content and behavior dictated that an entirely new web page be loaded in order to display new information.

It quickly became clear that a way of perfoming "client-side" or "web browser-side" processing was needed. The original intent for JavaScript, therefore, was to address this need by allowing such tasks as validating user input before it is transmitted to the web server, and creating dynamic web page content and layouts independently of the web server (for example displaying different text depending on a user's actions within the page).

JavaScript met and, indeed, exceeded these requirements by providing an extremely flexible and intuitive scripting language. The problem today is that, as with any useful technology, JavaScript has been used in ways never anticipated by its original authors. As a result, the potential uses of JavaScript have grown far beyond the needs of the average person looking to add dynamic behavior to web pages. The result of this is that JavaScript book authors also feel the need to cover every possible capability of JavaScript, often to the extent that the average JavaScript reference book now runs to over 1,000 pages.

The purpose of this book, therefore, is to provide the essentials of JavaScript so that anyone with a web site can use this powerful scripting language quickly and effectively without having to learn things that, whilst within the capabilities of JavaScript, aren't actually needed by the average web designer. That said, this book does not take any shortcuts. It provides detailed and indepth knowledge of all aspects of JavaScript from language basics through to advanced topics

This book is designed to provide a detailed and comprehensive, yet easy to follow, guide to developing powerful, dynamic web pages using JavaScript. It could be said that the object of JavaScript Essentials is to provide you with everything you need to use JavaScript, and nothing that you don't.

Intended Audience:

This book assumes that the reader has some experience in designing web pages using either HTML or XHTML. Experience using other programming languages is a benefit, but not a requirement when reading this book. Every effort has been made to carefully explain the concepts of JavaScript to make this book accessible to those with little or no programming experience. The early chapters of JavaScript Essentials cover the basics of the JavaScript scripting language with plenty of examples illustrating the topics covered and providing "cut and paste" solutions to common problems. Only once the basics are covered does the book go on to cover the more advanced topics.

It is hoped that after completing this book, the typical reader will be confidently adding dynamic, JavaScript powered content to their web sites.