Dojo: The Definitive Guide

Behavior

Core contains a lightweight extension that builds on top of query to provide a great way for decoupling events and DOM manipulations from an HTML placeholder via the behavior module. It may not be intuitively obvious at first, but the ability to define behavior for nodes irrespective of the markup itself can lend an immense of flexibility to a design. For example, it allows you to concisely accomplish tasks such as assigning click handlers to all anchor elements without knowing where or how many anchor elements there will be. You use the same CSS selectors you learned about in Table 5-1 to find the nodes for attaching behavior to, so the possibilities are almost endless.

The behavior module currently provides two API calls; the add method allows you to queue up a collection of behaviors, and the apply method actually triggers those behaviors:

dojo.behavior.add(/*Object*/ behaviorObject)
dojo.behavior.apply(  )

Basically, you use add to assign a new behavior to a collection of DOM nodes, but the behavior isn't actually reflected until you call apply. One of the reasons that it's a two-step process is because the pattern of performing multiple add operations before a final apply occurs lends itself to a lot of asynchronous communication patterns, described in Chapter 4.

Tip

Chapter 4 introduced a data structure called Deferred that is a staple in Dojo's IO subsystem. Deferred s provide the façade of having a thread available to operate on and lend themselves to successively applying ...