Geolocation.watchPosition()
Secure context: This feature is available only in secure contexts (HTTPS), in some or all supporting browsers.
  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.
Syntax
navigator.geolocation.watchPosition(success)
navigator.geolocation.watchPosition(success, error)
navigator.geolocation.watchPosition(success, error, options)
Parameters
- success
- 
    A callback function that takes a GeolocationPositionobject as an input parameter.
- errorOptional
- 
    An optional callback function that takes a GeolocationPositionErrorobject as an input parameter.
- optionsOptional
- 
    An optional object that provides configuration options for the location watch. See Geolocation.getCurrentPosition()for more details on possible options.
Return value
  An integer ID that identifies the registered handler.
  The ID can be passed to the Geolocation.clearWatch() to unregister the handler.
Examples
var id, target, options;
function success(pos) {
  var crd = pos.coords;
  if (target.latitude === crd.latitude && target.longitude === crd.longitude) {
    console.log('Congratulations, you reached the target');
    navigator.geolocation.clearWatch(id);
  }
}
function error(err) {
  console.warn('ERROR(' + err.code + '): ' + err.message);
}
target = {
  latitude : 0,
  longitude: 0
};
options = {
  enableHighAccuracy: false,
  timeout: 5000,
  maximumAge: 0
};
id = navigator.geolocation.watchPosition(success, error, options);
Specifications
| Specification | 
|---|
| Geolocation API # watchposition-method | 
Browser compatibility
BCD tables only load in the browser
See also
- Using the Geolocation API
- 
    The interface it belongs to, Geolocation, and the way to access it —Navigator.geolocation.
- The opposite operation: Geolocation.clearWatch()
- A similar method: Geolocation.getCurrentPosition()