Asynchronous Loading Google Map API

googlemap.js

angular.module('googleMapAPI', [])
  .config(function(googleMapServiceProvider) {
    googeMapServiceProvider.setLang('zh-HK');  // Configuration that loading Google Map API in Traditional Chinese
  })
  .provider('googleMapService', function () {
      var language = 'en-US';
      function loadScript($document, callback, success) {
          var scriptTag = $document.createElement('script');
          scriptTag.id = "google-map-script";
          scriptTag.type = "text/javascript";
          scriptTag.src = 'https://maps.googleapis.com/maps/api/js?libraries=geometry&sensor=false&callback=mapReady&region=HK&language=' + language;
          $document.getElementsByTagName('body')[0].appendChild(scriptTag);
      }

      this.setLang = function(lang) {
        language = lang;
      }

      this.$get = ['$document', '$q', '$window', function($document, $q, $window) {

          var deferred = $q.defer();
          loadScript($document[0]);

          $window.mapReady = (function(deferred) {
            return function() {
              deferred.resolve(google);
              delete $window.mapReady
            }
          })(deferred);

          return deferred.promise;
      }];

  })