trying to query for window.DeviceMotionEvent gives back a warning message "No device motion or orientation events will be fired until permission has been requested and granted.". I can't see API to request permission and this is a regression from iOS12 where this worked. This event is used to get critical information for 360 and VR applications. Also, the permission settings in the general device settings to allow access has been removed, as it seems, so I can't find a way to ask or set the permission.
<rdar://problem/55440172>
You need to use the DeviceOrientation / DeviceMotion API to request permission to access this data (with a user interaction), which will prompt the user. See: https://w3c.github.io/deviceorientation/spec-source-orientation.html#dom-deviceorientationevent-requestpermission https://w3c.github.io/deviceorientation/spec-source-orientation.html#dom-devicemotionevent-requestpermission It was standardized.