Javascript 如何在现有服务的基础上创建工厂

我正在学习angularjs，阅读有关服务和工厂的文章。这方面提供的一个例子是

在阅读本文时，我试图将服务转换为factory，这是指向的链接。但它仍然没有像预期的那样工作，我不确定我做错了什么

HTML

  <div ng-app="app">
      <div ng-controller="CalculatorController">
          Enter a number:
          <input type="number" ng-model="number" />
          <button ng-click="doSquare()">X<sup>2</sup></button>
          <button ng-click="doCube()">X<sup>3</sup></button>

          <div>Answer: {{answer}}</div>
      </div>
  </div>

---

出于某种原因，你抱怨它不能实例化“应用”模块，所以一切都失败了

无论如何，下面是一个工作示例的提琴：

请注意，您不需要调用

CalculatorService.calcFactory.cube

，而是调用

CalculatorService.cube

var app = angular.module('app', []);

app.factory('MathService', function() {
  var service = {};
  service.add = function(a, b) {
    return a + b
  };

  service.subtract = function(a, b) {
    return a - b
  };

  service.multiply = function(a, b) {
    return a * b
  };

  service.divide = function(a, b) {
    return a / b
  };

  return service;
});

app.factory('CalculatorService', function(MathService) {
  var service = {};
  service.square = function(a) {
    return MathService.multiply(a, a);
  };
  service.cube = function(a) {
    return MathService.multiply(a, MathService.multiply(a, a));
  };

  return service;

});

app.controller('CalculatorController', function($scope, CalculatorService) {

  $scope.doSquare = function() {
    $scope.answer = CalculatorService.square($scope.number);
  }

  $scope.doCube = function() {
    $scope.answer = CalculatorService.cube($scope.number);
  }
});

var app = angular.module('app', []);

app.factory('MathService', function() {
  var service = {};
  service.add = function(a, b) {
    return a + b
  };

  service.subtract = function(a, b) {
    return a - b
  };

  service.multiply = function(a, b) {
    return a * b
  };

  service.divide = function(a, b) {
    return a / b
  };

  return service;
});

app.factory('CalculatorService', function(MathService) {
  var service = {};
  service.square = function(a) {
    return MathService.multiply(a, a);
  };
  service.cube = function(a) {
    return MathService.multiply(a, MathService.multiply(a, a));
  };

  return service;

});

app.controller('CalculatorController', function($scope, CalculatorService) {

  $scope.doSquare = function() {
    $scope.answer = CalculatorService.square($scope.number);
  }

  $scope.doCube = function() {
    $scope.answer = CalculatorService.cube($scope.number);
  }
});