Chapter 1. Introduction to Ajax

Thanks for picking up a copy of my book. My goal for this book is not only to explore the technologies that define Ajax and how they come together to create powerful client-side interactions, but also to teach you how to create practical examples that can be reused in any other Ajax-enabled web application. These examples will be completely object oriented for the scalability and flexibility that is required in enterprise-level applications. This book consists of chapters that will guide you through individual Ajax examples, such as how to create a reusable Ajax engine, how to create Ajax-enabled components, and my personal favorite, how to connect to server-side languages with Ajax. Ajax requires supporting technologies such as XML (Extensible Markup Language) and JSON (JavaScript Object Notation) for the data-interchange and JavaScript and CSS (Cascading Style Sheets) for the data rendering and display; therefore we will be focusing on these technologies before we dive into the more complex world of Ajax. With the knowledge of front-end and back-end integration, you will learn how each example can be combined into a functional application; after all, Ajax does require knowledge of both since they become so tightly integrated. We will also cover common programming patterns that can be applied to Ajax to make development much quicker and cleaner. From there we will learn some best practices for securing our Ajax applications and creating intuitive user interactions, as well as message handling and other client-side data displays.

Ajax is an acronym for Asynchronous JavaScript and XML, and at its heart is the XMLHTTPRequest object, which is part of the XML DOM (Document Object Model). Since it is such a critical part of Ajax, let's take a brief look at the XML DOM to see how it fits in with the subjects that we will be covering.