The Geolocation method
watchPosition() method is used to register a handler function that will be called automatically each time the position of the device changes. You can also, optionally, specify an error handling callback function.
This method returns a watch ID value that then can be used to unregister the handler by passing it to the Geolocation.clearWatch() method.
successA callback function that takes a Position object as an input parameter.
errorOptional An optional callback function that takes a PositionError object as an input parameter.
optionsOptional An optional PositionOptions object that provides configuration options for the location watch.
If your application is running on KaiOS, please take a look at geolocation wake lock to keep your application getting position updates while in the background or screen off.