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This chapter is from the book

This chapter is from the book

Why Use AJAX?

As stated previously in this chapter, you can use AJAX to help provide a rich user experience. Of all the new, cool techniques and technologies that are available in Web 2.0 and rich Internet applications, AJAX is clearly the most widely used today. Should you use AJAX simply because it’s cool? The short answer is “No,” which is explained in the next section.

AJAX Rationale

Although the user experience that results from AJAX development patterns is a much richer experience, the rationale for utilizing AJAX is the total amount of traffic that is reduced from users accessing your web pages. When you have a web application with a large user base, using AJAX significantly increases the scalability of the application due to the amount of web traffic that is reduced every time a page is loaded.

The following list gives advantages and disadvantages of AJAX:


  • Reduced page bandwidth
  • Load page data on demand
  • Service-based approach to web development
  • Rich user experience


  • Unexpected browser functionality (when the user clicks the back or refresh button)
  • Business logic can exist in the JavaScript
  • Difficult to test with automated tools

Although this book highlights and focuses on the advantages of AJAX, several disadvantages should be noted. The first thing your users will notice is that when they click the refresh or back button in the browser, the page has a possibility of losing its state when the page reloads. This is a result of dynamically loading data on demand (which was one of the advantages of AJAX).

The second disadvantage of AJAX that you will see in the development world is actually JavaScript. You might wonder that if AJAX is initiated from client-side JavaScript, how can JavaScript be a disadvantage? The answer is that JavaScript eventually will be considered a disadvantage for AJAX in your web applications. Over time, you will be quite shocked at the amount of JavaScript that is required (which is an evolution throughout the lifecycle of your application) for AJAX functionality in your application. It will start out very small and clean, but can quickly spiral out of control.

From the architecture perspective, there is not a clean way to reverse-engineer JavaScript into an architecture model. An architecture document will probably define how a page should function, and there could be thousands of lines of JavaScript behind the scenes to enable this functionality. Depending on your environment and Software Development Lifecycle (SDLC), this could become a problem because it is very difficult to validate the JavaScript against the architecture models.

The third (and certainly not the last) disadvantage is the potential difficulty of testing AJAX functionality with automated tools. For example, Visual Studio Team Suite (VSTS) 2005 had limited support for AJAX when creating web tests. This problem was easily circumvented with tools such as Fiddler (http://www.fiddlertool.com/fiddler/), which helps you capture AJAX requests, which then can be loaded into the VSTS Web Test. It is important to note that these issues have been resolved in VSTS 2008.

This section is designed not to scare you away from AJAX, but to create an awareness of things that can affect you and your AJAX development experience. Best practices and warnings are highlighted in upcoming chapters so that you can be aware of the pitfalls that can show up in your applications.

In the next section, you learn the basics of implementing AJAX in your applications.

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