Are Angularjs services singleton?

Question

In the referenceI read:

Lastly, it is important to realize that all Angular services are application singletons. This means that there is only one instance of a given service per injector.

but with this simple code seems not to be a singleton

'use strict';             angular.module('animal', [])                 .factory('Animal',function(){                     return function(vocalization){                         return {                             vocalization:vocalization,                             vocalize : function () {                                 console.log('vocalize: ' + this.vocalization);                             }                         }                     }                 });                     angular.module('app', ['animal'])                     .factory('Dog', function (Animal) {                         return Animal('bark bark!');                     })                     .factory('Cat', function (Animal) {                         return Animal('meeeooooow');                     })                 .controller('MainCtrl',function($scope,Cat,Dog){                      $scope.cat = Cat;                      $scope.dog = Dog;                      console.log($scope.cat);                      console.log($scope.dog);                     //$scope.cat = Cat;                 }); 

I'm a little confused can you explain me what's the matter ?

UPDATE 1 May be I'm not the sharpest tool in the shed but afer the @Khanh TO reply it would be a better explanation in the reference it's not very clear.

UPDATE 2

'use strict';             angular.module('animal', [])                 .factory('Animal',function(){                         return {                             vocalization:'',                             vocalize : function () {                                 console.log('vocalize: ' + this.vocalization);                             }                         }                  });                 angular.module('dog', ['animal'])                     .factory('Dog', function (Animal) {                         Animal.vocalization = 'bark bark!';                         Animal.color = 'red';                         return Animal;                     });                  angular.module('cat', ['animal'])                    .factory('Cat', function (Animal) {                         Animal.vocalization = 'meowwww';                         Animal.color = 'white';                         return Animal;                     });                  angular.module('app', ['dog','cat'])                 .controller('MainCtrl',function($scope,Cat,Dog){                      $scope.cat = Cat;                      $scope.dog = Dog;                      console.log($scope.cat);                      console.log($scope.dog);                     //$scope.cat = Cat;                 }); 

BOOM it's a singleton !

UPDATE 3

But if you do like

'use strict';             angular.module('animal', [])                 .factory('Animal',function(){                     return function(vocalization){                         return {                             vocalization:vocalization,                             vocalize : function () {                                 console.log('vocalize: ' + this.vocalization);                             }                         }                     }                 });                     angular.module('app', ['animal'])                     .factory('Dog', function (Animal) {                         function ngDog(){                             this.prop = 'my prop 1';                             this.myMethod = function(){                                 console.log('test 1');                             }                         }                         return angular.extend(Animal('bark bark!'), new ngDog());                     })                     .factory('Cat', function (Animal) {                         function ngCat(){                             this.prop = 'my prop 2';                             this.myMethod = function(){                                 console.log('test 2');                             }                         }                         return angular.extend(Animal('meooow'), new ngCat());                     })                 .controller('MainCtrl',function($scope,Cat,Dog){                      $scope.cat = Cat;                      $scope.dog = Dog;                      console.log($scope.cat);                      console.log($scope.dog);                     //$scope.cat = Cat;                 }); 

it works

Answer 1

It's singleton, there is only one object, but is injected into many places. (objects are passed by reference to a method)

All your Animal are object pointers referring to the same animal object which is a function in your case. Your Cat and Dog are objects constructed by this function.

Answer 2

Yes, service is singleton. The following code log only one "M" to console:

function M() { console.log('M'); } function M1(m) { console.log(1); } function M2(m) { console.log(2); } angular.module('app', []) .service('M', M) .service('M1', ['M', M1]) .service('M2', ['M', M2]) .controller('MainCtrl',function(M1, M2){}); 

run it in jsbin