Beginning JavaScript, 5th Edition

14Ajax

WHAT YOU WILL LEARN IN THIS CHAPTER:                

• Making HTTP requests with the XMLHttpRequest object
• Writing a custom Ajax module
• Working with older Ajax techniques to preserve usability

WROX.COM CODE DOWNLOADS FOR THIS CHAPTER

You can find the wrox.com code downloads for this chapter at http://www.wiley.com/go/BeginningJavaScript5E on the Download Code tab. You can also view all of the examples and related files at http://beginningjs.com.

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, because 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 ...