问JavaScript地理定位误差-回调函数误差

EN

Uncaught TypeError: Failed to execute 'getCurrentPosition' on 'Geolocation': The callback provided as parameter 1 is not a function.

var app = {

  position: null,

  // Application Constructor
  initialize: function() {
    alert("app.initialize invoked");
    console.log("Initializing google map");
    $(document).ready(this.onDeviceReady); 
  },


  // Execute on success - when calling this function invoke with this. prefixed
  onSuccess: function() 
  {
    alert("app.onSuccess invoked");
    var lat = geolocation.coords.latitude;
    var lng = geolocation.coords.longitude;
    localStorage.setItem("Latitude", lat);
    localStorage.setItem("Longitude", lng);
    alert("lat: " + lat + "long: " + lng);
  },

  // Execute on failure - when calling this function invoke with this. prefixed
  onError: function() 
  {
    alert("Code: " + error.message);
  },


  // Execute on deviceReady - when calling this function invoke with this. prefixed
  onDeviceReady: function() 
  {
    alert("app.onDeviceReady invoked");
    var options = { enableHighAccuracy: true };
    alert("app.onDeviceReady invoked +2");

    //<------------------- vv Does not work vvv -------------------
    navigator.geolocation.watchPosition(this.onSuccess, this.onError, options);
    alert("app.onDeviceReady invoked +3");

  },



  // Attach google map to div
  showGoogleMap: function() 
  {

  } 

};

function onLoad() {
  alert("onLoad invoked");
  app.initialize();
}