Event handler for no objects as default.
The onMouseMove event handler is used to execute specified
the following properties of the Event
object: Because MouseMove events occur so often, it is not a default
event of any object. To use this event type wth an object you must explicitly
set the object to capture MouseMove events.
type - indicates the type of event.
target - indicates the target object to which the event was sent.
layerX, layerY, pageX, pageY, screenX, screenY
indicate the cursor location at the time of the MouseMove event.
which - 1 represents a left mouse click and 3 a right click.
modifiers - lists the modifier keys (shift, alt, ctrl, etc.) held down when the MouseMove event occurs.