Much has changed since the first edition of JavaScript Step by Step was written in 2007. The underlying JavaScript specification received a major update; Microsoft released Windows Internet Explorer 8—and now 9 (which is about to be released as I write this); JavaScript development frameworks have matured and are now ubiquitous; and browsers other than Internet Explorer and Firefox, such as Safari, Chrome, and mobile browsers, became much more popular.

This second edition of JavaScript Step by Step builds on the foundation laid down by the first edition. The underlying architecture of the JavaScript language is largely the same, but its use has become pervasive, increasing hugely even in just the last three years. With that in mind, the layout and coverage of the book have also remained largely the same, with two notable exceptions: this edition places a much greater emphasis on JavaScript event handling, and it includes an entirely new section covering JavaScript libraries. Specifically, the book focuses on jQuery, which can help simplify JavaScript development, especially on large projects.

Throughout the book, you’ll find highlights and additions for the new features in the latest version of JavaScript. Also, the examples used in the book received greater scrutiny, in multiple browsers, to reflect the reality of today's web landscape. Reader feedback from the first edition is reflected in the content and was the impetus for adding jQuery and emphasizing event handling.

The introduction to the first edition is still relevant and applicable, and so I’ve included it here.

JavaScript is an integral language for web application development, regardless of whether you’re adding interactivity to a web page or creating an entire application. Today’s web wouldn’t be the same without JavaScript.

JavaScript is a standards-based language with a formal specification; however, as any web developer will tell you, almost every web browser interprets that specification differently, which makes web developers’ jobs more difficult. Fortunately, most web browsers are converging in their support and interpretation of JavaScript’s core functions.

This book provides an introductory look at JavaScript, including some of its core functions as well as newer features and paradigms, such as Asynchronous JavaScript and XML (AJAX). Today’s web users rely on many different platforms and many different browsers to view web content. This fact was central to development of every aspect of the book, so you’ll see screenshots in multiple browsers and an emphasis on standards-based, rather than proprietary, JavaScript development.