Used to indicate whether the 'alt' key was depressed during the firing of the event.

  Used to indicate whether the 'alt' key was depressed during the firing
of the event. On some platforms this key may map to an alternative
key name.

  During mouse events caused by the depression or release of a mouse button, button is used to indicate which mouse button changed state.

  During mouse events caused by the depression or release of a mouse
button, button is used to indicate which mouse button
changed state. The values for button range from zero to
indicate the left button of the mouse, one to indicate the middle
button if present, and two to indicate the right button. For mice
configured for left handed use in which the button actions are
reversed the values are instead read from right to left.

The horizontal coordinate at which the event occurred relative to the DOM implementation's client area.

The vertical coordinate at which the event occurred relative to the DOM implementation's client area.

Used to indicate whether the 'ctrl' key was depressed during the firing of the event.

  Used to indicate whether the 'meta' key was depressed during the firing of the event.

  Used to indicate whether the 'meta' key was depressed during the firing
of the event. On some platforms this key may map to an alternative
key name.

  Used to identify a secondary EventTarget related to a UI event.

  Used to identify a secondary EventTarget related to a UI
event. Currently this attribute is used with the mouseover event to
indicate the EventTarget which the pointing device
exited and with the mouseout event to indicate the
EventTarget which the pointing device entered.

The horizontal coordinate at which the event occurred relative to the origin of the screen coordinate system.

The vertical coordinate at which the event occurred relative to the origin of the screen coordinate system.

Used to indicate whether the 'shift' key was depressed during the firing of the event.

  The initMouseEvent method is used to initialize the value of a MouseEvent created through the DocumentEvent interface.

  The initMouseEvent method is used to initialize the value
of a MouseEvent created through the
DocumentEvent interface. This method may only be called
before the MouseEvent has been dispatched via the
dispatchEvent method, though it may be called multiple
times during that phase if necessary. If called multiple times, the
final invocation takes precedence.
Parameters:
- typeArg - Specifies the event type.
- canBubbleArg - Specifies whether or not the event can bubble.
- cancelableArg - Specifies whether or not the event's default action can be prevented.
- viewArg - Specifies the Event's AbstractView.
- detailArg - Specifies the Event's mouse click count.
- screenXArg - Specifies the Event's screen x coordinate
- screenYArg - Specifies the Event's screen y coordinate
- clientXArg - Specifies the Event's client x coordinate
- clientYArg - Specifies the Event's client y coordinate
- ctrlKeyArg - Specifies whether or not control key was depressed during the Event.
- altKeyArg - Specifies whether or not alt key was depressed during the Event.
- shiftKeyArg - Specifies whether or not shift key was depressed during the Event.
- metaKeyArg - Specifies whether or not meta key was depressed during the Event.
- buttonArg - Specifies the Event's mouse button.
- relatedTargetArg - Specifies the Event's related EventTarget.