TodoService in Angular 2 and Angular 1 both in TypeScript and ES5 https://github.com/AngularClass/angular2-webpack-starter/blob/e6c03b9fd83426d4ac180c0969d08b1aef9cbd2e/src/app/services/TodoService.ts#L20

ng1.TodoService.es5.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;

}));
 

ng1.TodoService.ts

import angular from 'angular';

// Using TypeScript we can define our state interface
interface ITodo {
  value: string;
  created_at: Date;
  completed?: boolean;
}
interface ITodoState {
  todos: Array<ITodo>
}

// We can also make a TodoStore
var _todoState:ITodoState = {
  todos: [
    { value:'finish example', created_at: new Date() },
    { value:'add tests',      created_at: new Date() }
  ]
};

// Our Todo Service
export class TodoService {
  private _state: ITodoState; // we shouldn't access .state directly
  
  static $inject = ['todoState'];
  constructor(state) {
    this._state = state;
  }

  get(type) {
    return (type) ? this._state[type] : this._state;
  }

  add(todo) {
    this._state.todos.push({
      value: todo,
      created_at: new Date()
    });
  }

  remove(index) {
    this._state.todos.splice(index, 1);
  }

}//TodoService


var moduleName = 'app.services.todoservice';
export var ngModule = angular.
  module(moduleName, []).
  value('todoState', _todoState).
  service('TodoService', TodoService)

export default moduleName;

ng2.TodoService.es5.js

// <script src="angular2.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 ng = require('ng');
  var Inject = ng.Inject;
  var bind = ng.bind;

  // 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
  var TodoService = exports['TodoService'] = ng.
    Class({
      constructor: [new Inject('todoState'), function(state) {
        this.state = state;
      }],
      get: function(type) {
        return (type) ? this.state[type] : this.state;
      },
      add: function(todo) {
        this.state.todos.push({
          value: todo,
          created_at: new Date()
        });
      },
      remove: function(index) {
        this.state.todos.splice(index, 1);
      }
    });
  // TodoService 

  // Dependency injection
  var todoInjectables = exports['todoInjectables'] = [
    bind('initialTodoState').toValue(_todoState),
    bind(TodoService).toClass(TodoService),
    // We only have this to mimic Angular 1's di that is limited only to string tokens. Otherwise we would use `TodoService` class as the token
    bind('TodoService').toAlias(TodoService)
  ];

}));

ng2.TodoService.ts

import {bind, Inject} from 'angular2/di';

// Using TypeScript we can define our state interface
interface ITodo {
  value: string;
  created_at: Date;
  completed?: boolean;
}
interface ITodoState {
  todos: Array<ITodo>
}

// We can also make a TodoStore
var _todoState:ITodoState = {
  todos: [
    { value:'finish example', created_at: new Date() },
    { value:'add tests',      created_at: new Date() }
  ]
};

// Our Todo Service
@Injectable()
export class TodoService {
  private _state: ITodoState; // we shouldn't access .state directly
  
  constructor(@Inject('todoState') state) {
    this._state = state;
  }

  get(type) {
    return (type) ? this._state[type] : this._state;
  }

  add(todo) {
    this._state.todos.push({
      value: todo,
      created_at: new Date()
    });
  }

  remove(index) {
    this._state.todos.splice(index, 1);
  }

}//TodoService


export const todoInjectables = [
  bind('todoState').toValue(_todoState),
  bind(TodoService).toClass(TodoService),
  // We only have this to mimic Angular 1's di that is limited only to string tokens. Otherwise we would use `TodoService` class as the token
  bind('TodoService').toAlias(TodoService)
];