JavaScript 2.0-The Complete Reference, Second ... - freecodingtutorial

Table 21-12: Some Default Behaviors Available in Internet Explorer 5+
Behavior Description
>saveFavorite Enables the current state of the page to be saved when the page is
added to the user's list of ―Favorites.‖ Most often attached to a form
and very useful for a ―login‖ page.
>saveHistory Enables the current state of the page to be saved for the current
browsing session. Whenever the user navigates back to the page,
the page will be displayed with the saved state. Most often attached
to a form.
>saveSnapshot Enables the current state of the page to be saved when the user
saves the page to the local file system.
>userData Permits saving and retrieving large amounts of state information,
even across multiple browsing sessions.
As you can see, the default Behaviors are more related to browser functionality and state
information than to traditional DHTML. The interfaces they expose can be a bit complex, so we
will not get into the specifics of each (although an example of saving state information is
included at the end of Chapter 16, and browser capabilities were touched upon in Chapter 17).
Default Behaviors are attached to elements like any other Behavior, but the URL employed has
the form
#default#behaviorName
where behaviorName is the name of the default Behavior you wish to attach. For example, to
attach the userData Behavior to all form elements, you might use the following in your CSS
definitions:
form { behavior:url(#default#userData) }
Full documentation of default Behaviors can be found at MSDN.
Element Behaviors
Whereas attached Behaviors augment or override the normal behavior of an existing element,
element Behaviors are used to define new, customized elements. For instance, you can create
your own rollover element, define default Behaviors for it, and include it in your pages as if it
were a real part of HTML. You can even use attached Behaviors with new elements created in
this fashion.
Creating a custom element is like creating an attached Behavior. An HTC file is created using
almost exactly the same syntax as you would use to define an attached Behavior. However, an
element Behavior is imported into the page using XML, and after it has been imported, the new
element can be used directly in the page without explicit binding to the HTC file. Because the
HTC file defines the new element, there is no need to use addBehavior() or the CSS syntax
used for attached Behaviors; doing so would be redundant. In fact, it is not possible to bind an
element Behavior to an element as you would an attached Behavior.
Element Behaviors are tremendously powerful, and well beyond the scope of this book.
However, readers with an understanding of XML and the attached Behavior features discussed
previously should have little problem creating their own elements. Aside from the highly
nonstandard nature of element Behaviors, the only drawback of their use is that they are
supported only by Internet Explorer 5.5+. For the time being, it might be advisable to stick with
attached Behaviors until browser demographics shift heavily to newer versions of IE.
Behaviors Versus Traditional DHTML