controller.js

// service = {};

function controller(scope) {
  service.todo.get();
  // or $todo = service.todo
  // or require('todoService', function($todo) {}
};

jsService.js

service.todo = (function() {
  var todos = [
    { value:'finish example', created_at: new Date() },
    { value:'add tests',      created_at: new Date() }
  ];
  
  return {
    get: function() {
      return todos;
    },
    
    add: function(todo) {
      todos.push({
        value: todo,
        created_at: new Date()
      })
    },
    
    remove: function(index) {
      todos.splice(index, 1);
    }
  }
})();

ngService.js

// <script src="angular.min.js"></script>

(function(name, factory) {
  // our basic IO module system that stores every module on modules with the "file" namespace
  // please use something like browserify rather than rolling your own like this
  window.modules = window.modules || {};
  window.require = window.require || function require(name) { return window.modules[name] || window[name]; };
  var exports = {}; factory(exports, window.require);
  window.modules[name] = exports;
}('TodoService', function(exports, require) {
  var angular = require('require');

  // We can also make a TodoStore
  var _todoState = {
    todos: [
      { value:'finish example', created_at: new Date() },
      { value:'add tests',      created_at: new Date() }
    ]
  };
   
  // Our Todo Service
  TodoService.$inject = ['todoState'];
  exports['TodoService'] = function TodoService(state) {
    this.state = state;
  }

  TodoService.prototype.get = function get(type) {
    return (type) ? this.state[type] : this.state;
  }

  TodoService.prototype.add = function add(todo) {
    this.state.todos.push({
      value: todo,
      created_at: new Date()
    });
  }

  TodoService.prototype.remove = function remove(index) {
    this.state.todos.splice(index, 1);
  }
  // TodoService 
   
  // Dependency injection
  var moduleName = 'app.services.todoservice';
  exports['ngModule'] = angular.
    module(moduleName, []).
    value('todoState', _todoState).
    service('TodoService', TodoService)

  exports['name'] = moduleName;

}));