Javascript/扩展类/对象

Question

我已经为我的工作完成了一些任务，我已经完成了所有这些任务。但是我有一些问题，它不能按预期工作。当我尝试为 Customer 类添加新用户时，例如：

var user3 = new Customer ("Sergiu", "Tataru");

当我访问 user3 时，我收到：

lastname: undefined

为什么会这样？

查看结果以了解我的意思

我已经完成的任务：

1. 使用 Person 类并为 Employee 和 Customer 扩展它 类。
2. Person 对象具有私有名称属性和名称的 getter 方法。
3. Employee 类有两个私有属性租用日期和薪水。它还具有用于这两个属性的 getter 方法。
4. Customer 类具有私有合同编号属性和合同编号的 getter。

代码：

//4)Create a Person class
class Person{
  constructor(firstName, lastName) {
    this.firstname = firstName;
    this.lastname = lastName;
    var _name = name;// create a private name property for the Person class

  // create a getter method for the name for the Person class
    this.getName = function () {
      return _name;
    };

    this.getFullName = function() {
      return this.firstname+ " " + this.lastname;
    };
  }
}

// extend Person class for the Employee and Customer classes.
class Employee extends Person {
  constructor(hireDate, salary){

  super(hireDate, salary);
  var _hiredate = hireDate; // create a private property hire date for  Employee class
  var _salary = salary; // create a private property salary for  Employee class

  // create a getter method for the hire date s
  this.getHireDate = function(){
  return _hiredate;
};
  // create a getter method for the salary
  this.getSalary = function(){  //varianta alternativa:  Employee.prototype.getSalary = function(){
  return _salary;
};
}
}


class Customer extends Person {
constructor(contractNumber){

super(contractNumber);
var _contractNumber = contractNumber; // create a private contract number for Customer class


//create a  getter for the contract number.
this.getcontractNumber = function(){
return _contractNumber;
};
};
}

Answer 1

我认为您的super 通话存在一些问题。

//4)Create a Person class
class Person{
  constructor(firstName, lastName) {
    this.firstname = firstName;
    this.lastname = lastName;
    var _name = name;// create a private name property for the Person class

  // create a getter method for the name for the Person class
    this.getName = function () {
      return _name;
    };

    this.getFullName = function() {
      return this.firstname+ " " + this.lastname;
    };
  }
}

// extend Person class for the Employee and Customer classes.
class Employee extends Person {
  constructor(firstname, lastname, hireDate, salary){

  super(firstname, lastname);
  var _hiredate = hireDate; // create a private property hire date for  Employee class
  var _salary = salary; // create a private property salary for  Employee class

  // create a getter method for the hire date s
  this.getHireDate = function(){
  return _hiredate;
};
  // create a getter method for the salary
  this.getSalary = function(){  //varianta alternativa:  Employee.prototype.getSalary = function(){
  return _salary;
};
}
}


class Customer extends Person {
constructor(firstname, lastname, contractNumber){

super(firstname, lastname);
var _contractNumber = contractNumber; // create a private contract number for Customer class


//create a  getter for the contract number.
this.getcontractNumber = function(){
return _contractNumber;
};
};
}

var user3 = new Customer ("Sergiu", "Tataru", 999);
console.log(user3.lastname)

Answer 2

你打电话：

var user3 = new Customer ("Sergiu", "Tataru");

但是客户的构造函数的参数是contractNumber，所以没有定义姓氏是很正常的。

这个构造函数使用contractNumber调用Person的构造函数，所以你应该在firstname中找到这个值（这里是'Sergiu'），但lastname中没有传递任何内容。

编辑

你应该这样做：

class Customer extends Person {
constructor(firstname, lastname, contractNumber){

super(firstname, lastname);
var _contractNumber = contractNumber; // create a private contract number for Customer class


//create a  getter for the contract number.
this.getcontractNumber = function(){
return _contractNumber;
};
};
}

查看构造函数接口和super 调用。