Tech Stuff - DOM Events

W3C Event Reference. Part of the Events Interface.

Events

The following notes apply:

Events bubble UP. Event listeners may be registered at various levels in the object hierarchy for the same event.
Events may be canceled at any level (if allowed).
We use the terms properties - W3C use the term attributes.
We use the term object - W3C use the term element.
EventTarget is the object in object.addEventListener(params).
DOM-2 does not define keyboard events.
Mutation events are triggered when the page is changed.

Event Properties

The following properties (attributes) are exposed when an event is triggered (an event object is created). ALL properties (attributes) below are READ ONLY.

Property	Description
altKey	boolean - true if alt key pressed
button	0 = right, 1 = middle, 2 = left. More than one button may be indicated. In Gecko not valid on mousemove, mouseout, mouseover.
clientX	the horizontal offset in pixels from the parent node of this object.
clientY	the vertical offset in pixels from the parent node of this object.
ctrlKey	boolean - true = control key pressed.
metaKey	boolean true = meta key pressed.
relatedTarget	on 'mouseover' should be object being exited. For 'mouseout' should be the object being entered.
screenX	the horizontal offset in pixels from the origin of the screen.
screenY	the vertical offset in pixels from the origin of the screen.
shiftKey	boolean true = shift key was pressed.
bubbles	boolean true = event can bubble.
cancelable	boolean true = event can be canceled.
currentTarget	the name of the object currently being processed.
eventPhase	may be: AT_TARGET - evaluation (being initialised) BUBBLING_PHASE CAPTURING_PHASE.
target	indicates the target to which the event was originally dispatched.
timeStamp	time in milliseconds from 1st January 1970 (UCT) or 0 if not available.
type	the name of the event.
detail	event specific details.
view	identifies the AbstractView for the event (?).
attrChange	Mutation. Indicates the type of change may be: ADDITION, MODIFICATION, REMOVAL.
attrName	Mutation. The name of object that changed.
newValue	Mutation. The new value of the object.
prevValue	Mutation. The previous value of the object.
relatedNode	Mutation. Indicates the actual node changed if an indirect event was created (the event was triggered by a change to another node which may be higher or lower in the hierarchy).

Event Methods

The following methods are exposed when an event is triggered (an event object is created).

Method	Description
addEventListener	adds an event listener for the defined event type for the specified object.
dispatchevent	fires an event created by a createEvent followed by an initEvent.
removeEventListener	removes an event listener for the defined event type for the specified object.
initEvent	initialises an event that is subsequently fired by the dispatchEvent method.
preventDefault	stops the event bubbling (this lets you stop the default context menu on right mouse click).
stopPropagation	stops further event triggering at higher levels in the object hierarchy (this lets you stop the default context menu on right mouse click).
createEvent	called as part of a sequence to fire an event createEvent->initMouseEvent->dispatchevent.
initUIEvent	initialises a UI event that is subsequently fired by the dispatchEvent method.
initMouseEvent	initialises a Mouse event that is subsequently fired by the dispatchEvent method.
initMutationEvent	initialises a Mutation event that is subsequently fired by the dispatchEvent method.

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