javascript event Description

The Netscape 6 event object is more complex in some ways due to the object-oriented nature of the underlying W3C DOM Event object structure. Rather than being an all-encompassing object (as the IE event object is), the Netscape 6 event object exposes different sets of properties and methods depending on the classification of event. All event classes share the properties and methods of the W3C DOM root Event object. But actual event object instances belong to one of the Event object's subclasses (and sometimes, sub-subclasses). These subclasses are known as UIEvent (so-called user interface events such as DOMFocusIn), MouseEvent (including the well-known mouse events), MutationEvent (events that signal a scripted change to the node structure of the document), and, coming in DOM Level 3, TextEvent (keyboard-related events). Netscape 6 implements its own, temporary keyboard events classification under the name KeyEvent, which is a subclass of UIEvent, although it borrows some MouseEvent properties for scripting convenience.

By and large, this functional division of objects won't impact your Netscape 6 event processing because an event listener function for a particular kind of event will be looking for properties associated with that event. The event class is of little concern. Still, it is instructive to see the way event object properties and methods cascade through this object-oriented structure. The following table illustrates the distribution of properties among Netscape 6 and W3C DOM event classes.

And the following table illustrates the distribution of methods among Netscape 6 and W3C DOM event classes.

The event object in Netscape 6 also implements the properties of the Navigator 4 static Event object, and it inherits an enormous list of W3C DOM TextEvent object constants that represent nonalphanumeric keyboard key codes (which have constant names like eventObject.DOM_VK_PAGE_UP). These keyboard constants are defined in the forthcoming W3C DOM Level 3 events module, but are already implemented in Netscape 6 (although the values don't exactly line up yet). A list of properties for the Navigator 4 static Event object appears in the Event object discussion following the current foray through an instance of an event.

You must use different script techniques to obtain a reference to an event object in the IE and Navigator event models. Once you have that reference, you are well on your way to equalizing event processing across browsers. The example fragments that follow assume that previous script statements have obtained a reference to the browser-specific event object (usually shown in the example as stored in a variable called evt).

• eventObj
• [window.]event

None.