The following constant defines the one legal value for the code property of an EventException object. Note that this constant is a static property of EventException, not a property of individual exception objects.
unsigned short UNSPECIFIED_EVENT_TYPE_ERR = 0
An Event object has a type property that is uninitialized, or is null or the empty string.
unsigned short code
An error code that provides some detail about what caused the exception. In the Level 2 DOM there is only one possible value for this field, defined by the constant above.
An EventException is thrown by certain event-related methods to signal a problem of some sort. (In the DOM Level 2 specification, an exception of this type is thrown only by EventTarget.dispatchEvent( )).