WheelEvent

The WheelEvent interface represents events that occur due to the user moving a mouse wheel or similar input device.

Note: This is the standard wheel event interface to use. Old versions of browsers implemented the non-standard and non-cross-browser-compatible MouseWheelEvent and MouseScrollEvent interfaces. Use this interface and avoid the non-standard ones.

Don't confuse the wheel event with the scroll event:

  • A wheel event doesn't necessarily dispatch a scroll event. For example, the element may be unscrollable at all. Zooming actions using the wheel or trackpad also fire wheel events.
  • A scroll event isn't necessarily triggered by a wheel event. Elements can also be scrolled by using the keyboard, dragging a scrollbar, or using JavaScript.
  • Even when the wheel event does trigger scrolling, the delta* values in the wheel event don't necessarily reflect the content's scrolling direction.
Event UIEvent MouseEvent WheelEvent

Constructor

WheelEvent()

Creates a WheelEvent object.

Instance properties

This interface inherits properties from its ancestors, MouseEvent, UIEvent, and Event.

WheelEvent.deltaX Read only

Returns a double representing the horizontal scroll amount.

WheelEvent.deltaY Read only

Returns a double representing the vertical scroll amount.

WheelEvent.deltaZ Read only

Returns a double representing the scroll amount for the z-axis.

WheelEvent.deltaMode Read only

Returns an unsigned long representing the unit of the delta* values' scroll amount. Permitted values are:

Constant Value Description
WheelEvent.DOM_DELTA_PIXEL 0x00 The delta* values are specified in pixels.
WheelEvent.DOM_DELTA_LINE 0x01 The delta* values are specified in lines. Each mouse click scrolls a line of content, where the method used to calculate line height is browser dependent.
WheelEvent.DOM_DELTA_PAGE 0x02 The delta* values are specified in pages. Each mouse click scrolls a page of content.
WheelEvent.wheelDelta Read only

Returns an integer (32-bit) representing the distance in pixels.

WheelEvent.wheelDeltaX Read only

Returns an integer representing the horizontal scroll amount.

WheelEvent.wheelDeltaY Read only

Returns an integer representing the vertical scroll amount.

Note: Element: mousewheel event has additional documentation about the deprecated properties wheelDelta, wheelDeltaX, wheelDeltaY.

Instance methods

This interface doesn't define any specific methods, but inherits methods from its ancestors, MouseEvent, UIEvent, and Event.

Specifications

Specification
UI Events
# interface-wheelevent

Browser compatibility

BCD tables only load in the browser

See also