AngularJS does not provide any mechanism to implement inheritance of services directly, however for your case you can use $provide.decorator to extend BaseService itself or use it like a prototype of another ChildService using plain JavaScript. In my practice, in order to have service with configurable state and behaviour I use providers. In all of the following examples the console output will be World.

Decorator

If you don't need the original BaseService in your module, you can decorate it

Plunker

function AlertService() {

  this.add = function(level, message) {

    switch(level) {

      case 'success':

        console.log(message);

    }

  }

}



function BaseService(alertService) {

  this.message =  Hello;

  this.perform = function () {

    alertService.add(success,this.message);

  };

}



angular.

  module('app',[]).

  config(['$provide', function($provide) {

    $provide.decorator('BaseService', function($delegate) {

      $delegate.message = 'World';

      return $delegate;

    });

  }]).

  service('alertService', AlertService).

  service('BaseService', ['alertService',BaseService]).

  controller('ctrl', ['BaseService', function(baseService) {

    baseService.perform();

  }]);

Prototypical Inheritance

Plunker

function AlertService() {

  this.add = function(level, message) {

    switch(level) {

      case 'success':

        console.log(message);

    }

  }

}



function BaseService(alertService) {

  this.message =  Hello;

  this.perform = function () {

    alertService.add(success,this.message);

  };

}



function ChildService(BaseService) {

  angular.extend(ChildService.prototype, BaseService);

  this.message = World;

}



angular.

  module('app',[]).

  service('alertService', AlertService).

  service('BaseService', ['alertService',BaseService]).

  service('ChildService', ['BaseService',ChildService]).

  controller('ctrl', ['ChildService', function(ChildService) {

    ChildService.perform();

  }]); 

Provider

Plunker

function AlertService() {

  this.add = function(level, message) {

    switch(level) {

      case 'success':

        console.log(message);

    }

  }

}



function BaseService() {

  var message =  Hello;



  this.setMessage = function(msg) {

    message = msg;

  }



  function Service(alertService) {

    this.perform = function () {

      alertService.add(success, message);

    };

  }



  function Factory(alertService) {

    return new Service(alertService);

  }



  this.$get = ['AlertService', Factory];

}



angular.

  module('app',[]).

  provider('BaseService', BaseService).

  config(['BaseServiceProvider', function(baseServiceProvider) {

    baseServiceProvider.setMessage('World');

  }]).

  service('AlertService', AlertService).

  controller('ctrl', ['BaseService', function(baseService) {

    baseService.perform();

  }]);