The Event object serves to provide both details about an event and control over the propagation of an event. DOM Level 2 defines a standard Event object, but Internet Explorer 4, 5, and 6 use a proprietary object instead. Netscape 4 has its own proprietary object that is different from the other two. DOM Level 2 does not standardize keyboard events, so the Netscape 4 Event object may be still useful to programmers interested in key events in Netscape 6 and later. The properties of the DOM, IE, and Netscape 4 Event objects are listed in separate sections below.

In the DOM and Netscape event models, an Event object is passed as an argument to the event handler. In the IE event model, the Event object that describes the most recent event is instead stored in the event property of the Window object.

DOM Constants

These constants are the legal values of the eventPhase property; they represent the current phase of event propagation for this event.


The event is in its capturing phase.

Event.AT_TARGET = 2

The event is being handled by its target node.


The event is bubbling.

DOM Properties

All properties of this object are read-only.


true if the Alt key was held down when an event occurred. Defined for mouse events.


true if the event is of a type that bubbles; false otherwise. Defined for all events.


Specifies which mouse button changed state during a mousedown, mouseup, or click event. 0 indicates the left button, ...

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