html5 geolocation with fallback.

gistfile1.js

// geo-location shim

// currentely only serves lat/long
// depends on jQuery

// doublecheck the ClientLocation results because it may returning null results

;(function(geolocation){

  if (geolocation) return;
  
  var cache;
  
  geolocation = window.navigator.geolocation = {};
  geolocation.getCurrentPosition = function(callback){
    
    if (cache) callback(cache);
    
    $.getScript('//www.google.com/jsapi',function(){
      
     // sometimes ClientLocation comes back null
     if (google.loader.ClientLocation) {
      cache = {
        coords : {
          "latitude": google.loader.ClientLocation.latitude, 
          "longitude": google.loader.ClientLocation.longitude
        }
      };
     }
      
      callback(cache);
    });
    
  };
  
  geolocation.watchPosition = geolocation.getCurrentPosition;

})(navigator.geolocation);



// usage
navigator.geolocation.watchPosition(function(pos){
  console.log("I'm located at ",pos.coords.latitude,' and ',pos.coords.longitude);
});

@paulirish actually, ignore my above comment. I investigated further how geolocation actually works (e.g. gets location of ip address, then triangulates user location based on nearby wifi hotspots) and realised that the fallbacks can only then work by getting the location of the ip address and the application I'm working on depends on the user location being accurate. So in my instance I can only really support genuine geolocation/GPS capable devices. Annoying still though that IE9's implementation is not accurate compared to other devices as it means an IE9 user may end up using the app even though it wont work correctly for them (e.g. browser sniff time? FUGLY)

Hi, I am getting an error on line 21/22.

Error: error: 'google.loader.ClientLocation.latitude' is null or not an object

Im running the following on page load:

function initialize() {
Modernizr.load({
test: Modernizr.geolocation,
nope: 'js/geolocation.js',
complete: initializeMap()
});
}

and have the following scripts attached to my page:

modernizr.custom.65531.js
//ajax.googleapis.com/ajax/libs/jquery/1.7.2/jquery.min.js
//maps.google.com/maps/api/js?sensor=true

Any insights as to what the problem may be?

@vancefsmith internet connection problem would be my best guess. The shim downloads a script from google to access the 'google' javascript API objects.

@vancefsmith and @LucisFerre I would not recommend using this polyfill. As far as I can tell, google.loader.ClientLocation is no longer supported and always returns null. See http://grokbase.com/t/gg/google-ajax-search-api/126whx58ap/google-loader-api-not-working or Google "google.loader.ClientLocation is always null."

At minimum, I would wrap 19-24 in a conditional:

if (google.loader.ClientLocation) {
    cache = {
        coords: {
            "latitude": google.loader.ClientLocation.latitude,
            "longitude": google.loader.ClientLocation.longitude
        }
    };
}

added your conditional, jeffrey and made mention about the null values at the top.

I mostly agree with you that this polyfill is of questionable value these days.