Touch

Limited availability

This feature is not Baseline because it does not work in some of the most widely-used browsers.

TheTouch interface represents a single contact point on a touch-sensitive device. The contact point is commonly a finger or stylus and the device may be a touchscreen or trackpad.

TheTouch.radiusX,Touch.radiusY, andTouch.rotationAngle describe the area of contact between the user and the screen, thetouch area. This can be helpful when dealing with imprecise pointing devices such as fingers. These values are set to describe an ellipse that as closely as possible matches the entire area of contact (such as the user's fingertip).

Note:Many of the properties' values are hardware-dependent; for example, if the device doesn't have a way to detect the amount of pressure placed on the surface, theforce value will always be 0. This may also be the case forradiusX andradiusY; if the hardware reports only a single point, these values will be 1.

Constructor

Touch(): Creates a Touch object.

Instance properties

This interface has no parent, and doesn't inherit or implement other properties.

Basic properties

Touch.identifierRead only: Returns a unique identifier for thisTouch object. A given touch point (say, by a finger) will have the same identifier for the duration of its movement around the surface. This lets you ensure that you're tracking the same touch all the time.
Touch.screenXRead only: Returns the X coordinate of the touch point relative to the left edge of the screen.
Touch.screenYRead only: Returns the Y coordinate of the touch point relative to the top edge of the screen.
Touch.clientXRead only: Returns the X coordinate of the touch point relative to the left edge of the browser viewport, not including any scroll offset.
Touch.clientYRead only: Returns the Y coordinate of the touch point relative to the top edge of the browser viewport, not including any scroll offset.
Touch.pageXRead only: Returns the X coordinate of the touch point relative to the left edge of the document. UnlikeclientX, this value includes the horizontal scroll offset, if any.
Touch.pageYRead only: Returns the Y coordinate of the touch point relative to the top of the document. UnlikeclientY, this value includes the vertical scroll offset, if any.
Touch.targetRead only: Returns theElement on which the touch point started when it was first placed on the surface, even if the touch point has since moved outside the interactive area of that element or even been removed from the document.

Touch area

Touch.radiusXRead only: Returns the X radius of the ellipse that most closely circumscribes the area of contact with the screen. The value is in pixels of the same scale asscreenX.
Touch.radiusYRead only: Returns the Y radius of the ellipse that most closely circumscribes the area of contact with the screen. The value is in pixels of the same scale asscreenY.
Touch.rotationAngleRead only: Returns the angle (in degrees) that the ellipse described by radiusX and radiusY must be rotated, clockwise, to most accurately cover the area of contact between the user and the surface.
Touch.forceRead only: Returns the amount of pressure being applied to the surface by the user, as afloat between0.0 (no pressure) and1.0 (maximum pressure).