Datasheet

Invisible Data Retrieval

The longer you look at a web page, the greater its chance to go out of date. With an Ajax application,

even though on the surface the web page might not be told to do anything, it could be updating itself

behind the scenes.

Constant Updating

Because you’re not waiting for a page refresh every time, and because Ajax can retrieve data under the

covers, the web application can be constantly updated. A traditional software application such as Word

or Outlook will alter the menus it displays or the views it shows, dependent on its configuration, or the

data it holds or the situation or circumstances it finds itself in. It doesn’t have to wait for a server or user

to perform an action before it can download new mail or apply a new template. Ajax techniques enable

web applications to behave more like Windows applications because of this.

Smooth Interfaces

An interface that doesn’t have to be changed is almost inevitably a user interface that is easier to use.

Ajax can cut both ways here in that you can use it to modify parts of the interface and simply confuse

users by changing the ground beneath their feet. In theory, by making subtle alterations, you could aid

the user’s passage through an interface or wizard and speed up the process.

Simplicity and Rich Functionality

As shown in the previous examples, some of the most impressive Ajax applications are those where you

had to look for the Ajax functionality, such as Basecamp. If Ajax can be used to make your applications

simpler while improving the user’s experience, then that must be an improvement.

Drag and Drop

Drag-and-drop functionality is one of the neatest features of most software applications, from Windows

Explorer to Windows Desktop. It doesn’t strictly qualify as Ajax functionality. It’s something that’s been

possible for a great many years in web applications, even before the introduction of the

XMLHttp

Request

object. Most developers seem to opt for Flash or some similarly heavyweight solution rather

than using the JavaScript and DOM solutions. In the reassessment of user-interface creation techniques

that Ajax has introduced, drag-and-drop functionality can be used to manage front-end changes, and

then these changes are submitted via Ajax to the server. For example, you drag several items on the

screen into new positions, and then you log out. Later, when you come back, those items are located in

the same positions.

With such a host of benefits, it might be difficult to imagine why everyone isn’t switching over to using

Ajax applications. There are definitely quite a few pitfalls, though, to consider.

When Not to Use Ajax

Once you’ve learned Ajax techniques, you shouldn’t go back and tear up all your old web pages and

start again. Rather, you should consider how you could improve the usability of your pages and

whether Ajax is a solution that will help improve them. Without advances in usability, you might as well

not bother at all.

Chapter 1: Introducing Ajax

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