Now, in Firefox, if the Event.Type is "mouse-something" (i.e. mouseover, mouseenter, mouseleave etc.), the isDefaultPrevented() will always set true, no matter whether event.preventDefault() is called or not. However, for Chrome and IE, the isDefaultPrevented() will be false if event.preventDefault() is not ever called.
I'm not sure if this is a bug or designed by purpose.
So my problem is, is there a way to determine whether preventDefault() is called for mouse-xxxx events?