This feature is non-standard and is not on a standards track. Do not use it on production sites facing the Web: it will not work for every user. There may also be large incompatibilities between implementations and the behavior may change in the future.
The DOM MouseScrollEvent represents events that occur due to the user moving a mouse wheel or similar input device.
Use standardardized WheelEvent instead of this legacy event object if available.
void initMouseScrollEvent(in DOMString typeArg, in boolean canBubbleArg, in boolean cancelableArg, in nsIDOMAbstractView viewArg, in long detailArg, in long screenXArg, in long screenYArg, in long clientXArg, in long clientYArg, in boolean ctrlKeyArg, in boolean altKeyArg, in boolean shiftKeyArg, in boolean metaKeyArg, in unsigned short buttonArg, in nsIDOMEventTarget relatedTargetArg, in long axis);
Indicates scroll direction. Read only.
The event is caused by horizontal wheel operation.