Beginning JavaScript®, Fourth Edition

Chapter 14. Ajax

Since its inception, the Internet has used a transaction-like communication model; a browser sends a request to a server, which sends a response back to the browser, which (re)loads the page. This is typical HTTP communication, and it was designed to be this way. But this model is rather cumbersome for developers, as it requires web applications to consist of several pages. The resulting user experience becomes disjointed and interrupted due to these separate page loads.

In the early 2000s, a movement began to look for and develop new techniques to enhance the user's experience; to make Web applications behave more like conventional applications. These new techniques offered the performance and usability usually associated with conventional desktop applications. It wasn't long before developers began to refine these processes to offer richer functionality to the user.

At the heart of this movement was one language: JavaScript, and its ability to make HTTP requests transparent to the user.

What Is Ajax?

Essentially, Ajax allows client-side JavaScript to request and receive data from a server without refreshing the web page. This technique enables the developer to create an application that is uninterrupted, making only portions of the page reload with new data.

The term Ajax was originally coined by Jesse James Garrett in 2005. He wrote an article entitled "Ajax: A New Approach to Web Applications" (www.adaptivepath.com/publications/essays/archives/000385.php). In it, ...