Javascript /擴展類/對象

Question

我爲我的工作做了一些任務，我完成了所有這些任務。但是我有一些問題，它不能像預期的那樣工作。當我嘗試添加一個新用戶的客戶類，例如：

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

當我訪問用戶3，我收到：

lastname: undefined 

爲什麼會這樣？

看到的結果，以明白我的意思

，我已經完成了任務：

1. 使用一個Person類並擴展它的員工和客戶 類。
2. Person對象具有專用名稱屬性和名稱的getter方法。
3. 僱員類有兩個私人物業僱用日期和工資。它也有兩個屬性的getter方法。
4. Customer類別具有私人合約號碼屬性和合約號碼的獲取者。

代碼：

//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

我覺得有一些問題，你super電話。

//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

您致電：

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

，但客戶的構造函數的參數是contractNumber，所以這是很正常的現象是沒有定義的姓氏。

該構造函數使用contractNumber調用Person的構造函數，因此您應該在名字中找到此值（'Sergiu'），但在姓氏中沒有任何值傳遞。

編輯

你應該做這樣的事情：

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; 
}; 
}; 
} 

看看構造函數接口，並在super電話。