Ajax Design Patterns

Chapter 7. Dynamic Behavior

With the technologies covered so far, we can change the display and talk to the server. But what will trigger these actions? Ajax Apps are generally driven from within the browser, so that’s where the actions will be triggered. Broadly speaking, there are two types of triggers, each covered here: User Actions, such as mouse clicks and keypresses, and Scheduling, where actions are scheduled to be run at some point in the future.

User Action

⊙⊙⊙ Action, Change, Click, Control, DHTML, DOM, Events, Keyboard, Mouse, Move, Type, Widget

Figure 7-1. User Action

Goal Story

Pam is booking a trip on the corporate travel planner. She sees a form with the usual fields and clicks on location. Suddenly, a list of cities fades in beside the form, and Pam selects Paris. Beside the city list, a second list appears, this one showing approved hotels. Pam chooses the Hilton, and both lists disappear. Pam’s pleased to proceed with the destination on the updated form, which now reads, “Paris Hilton.”

Problem

How can the application respond to user activity?

Forces

• A rich application allows users to interact with it, frequently and in different ways.

• Responses must be as quick as possible, so as to streamline performance, keep user attention, and help the user understand the application’s cause-effect model.

• Using form submissions as the only response to user activity is slow and limits ...