Creates a new MouseEvent of the specified
type and initial properties.
The bitwise combinations of mouse buttons pressed.
1 is the primary (left) button.
2 is the secondary (right) button.
4 is the middle button. Will be
0 when no buttons are pressed. See also
Only applies to focusin, focusout, mouseenter, mouseleave, mouseout, mouseover, dragenter, and dragexit events. It is the element that the receives the opposite event pair for this event. For example, the
relatedTarget of a mouseenter is the element that will receive the mouseleave event.