This feature has been removed from the Web standards. Though some browsers may still support it, it is in the process of being dropped. Do not use it in old or new projects. Pages or Web apps using it may break at any time.
Returns the orientation in degrees (in 90-degree increments) of the viewport relative to the device's natural orientation.
Its only possible values are
180. Positive values are clockwise; negative values are counterclockwise.
|Web Compatibility Standard
The definition of 'Window.orientation' in that specification.