JS原型和继承

Question

在我的业余时间，我尝试学习一点JS，但我坚持主题的主题。

var person = new Person("Bob", "Smith", 52); 
 
var teacher = new Teacher("Adam", "Greff", 209); 
 

 
function Humans(firstName, lastName) { 
 
    this.firstName = firstName; 
 
    this.lastName = lastName; 
 
} 
 

 
function Person(firstName, lastName, age) { 
 
    Humans.call(this, firstName, lastName); 
 
    this.age = age; 
 
} 
 

 
Person.prototype = Object.create(Humans.prototype); 
 

 
Person.prototype.fullDetail = function() { 
 
    return this.firstName + " " + this.lastName + " " + this.age; 
 
}; 
 

 

 
function Teacher(firstName, lastName, roomNumber) { 
 
    Humans.call(this, firstName, lastName); 
 
    this.room = roomNumber; 
 
} 
 

 
Teacher.prototype = Object.create(Humans.prototype); 
 

 
Teacher.prototype.fullDetail = function() { 
 
    return this.firstName + " " + this.lastName + " " + this.room; 
 
}; 
 

 
person.fullDetail();

任何人能告诉我，为什么我不能执行person.fullDetail();？

如果您可以对您的代码版本进行一些评论，我将非常感激，谢谢。

Answer 1

因为你”在定义原型应该是什么之前重新创建对象。

当你

var person = new Person ("Bob", "Smith", 52); 

你的基础上 Person的 当前定义制作的对象

。后来在该代码，你改变的Person原型在它的全部

Person.prototype = Object.create(Humans.prototype); 

为了解决这个问题，创建对象后，你就大功告成了重新分配的雏形。

function Humans(firstName, lastName) { 
 
    this.firstName = firstName; 
 
    this.lastName = lastName; 
 
} 
 

 
function Person(firstName, lastName, age) { 
 
    Humans.call(this, firstName, lastName); 
 
    this.age = age; 
 
} 
 

 
Person.prototype = Object.create(Humans.prototype); 
 

 
Person.prototype.fullDetail = function() { 
 
    return this.firstName + " " + this.lastName + " " + this.age; 
 
}; 
 

 

 
function Teacher(firstName, lastName, roomNumber) { 
 
    Humans.call(this, firstName, lastName); 
 
    this.room = roomNumber; 
 
} 
 

 
Teacher.prototype = Object.create(Humans.prototype); 
 

 
Teacher.prototype.fullDetail = function() { 
 
    return this.firstName + " " + this.lastName + " " + this.room; 
 
}; 
 

 
var person = new Person("Bob", "Smith", 52); 
 
var teacher = new Teacher("Adam", "Greff", 209); 
 
console.log(person.fullDetail());

Answer 2

是的，这是因为当你创建person对象Person原型没有FullDetail方法。

更改你的对象创建的排序，创建Person对象添加方法后以原形

检查这个片段

var teacher; 
 
var person; 
 
function Humans(firstName, lastName) { 
 
    this.firstName = firstName; 
 
    this.lastName = lastName; 
 
} 
 

 
function Person(firstName, lastName, age) { 
 
    Humans.call(this, firstName, lastName); 
 
    this.age = age; 
 
} 
 

 
Person.prototype = Object.create(Humans.prototype); 
 

 
Person.prototype.fullDetail = function() { 
 
    return this.firstName + " " + this.lastName + " " + this.age; 
 
}; 
 

 
person = new Person("Bob", "Smith", 52); 
 

 
function Teacher(firstName, lastName, roomNumber) { 
 
    Humans.call(this, firstName, lastName); 
 
    this.room = roomNumber; 
 
} 
 

 
Teacher.prototype = Object.create(Humans.prototype); 
 

 
Teacher.prototype.fullDetail = function() { 
 
    return this.firstName + " " + this.lastName + " " + this.room; 
 
}; 
 
teacher= new Teacher("Adam", "Greff", 209); 
 
console.log(person.fullDetail()); 
 
console.log(teacher.fullDetail());

希望它可以帮助

Answer 3

我想这是因为你无需在原型尚未定义它们的功能创建者和教师。试试这个：

function Humans(firstName, lastName) { 
 
     this.firstName = firstName; 
 
     this.lastName = lastName; 
 
    } 
 
    
 
    function Person(firstName, lastName, age) { 
 
     Humans.call(this, firstName, lastName); 
 
     this.age = age; 
 
    } 
 
    
 
    Person.prototype = Object.create(Humans.prototype); 
 
    
 
    Person.prototype.fullDetail = function() { 
 
     return this.firstName + " " + this.lastName + " " + this.age; 
 
    }; 
 
    
 
    
 
    function Teacher(firstName, lastName, roomNumber) { 
 
     Humans.call(this, firstName, lastName); 
 
     this.room = roomNumber; 
 
    } 
 
    
 
    Teacher.prototype = Object.create(Humans.prototype); 
 
    
 
    Teacher.prototype.fullDetail = function() { 
 
     return this.firstName + " " + this.lastName + " " + this.room; 
 
    }; 
 
    var person = new Person ("Bob", "Smith", 52); 
 
    var teacher = new Teacher ("Adam", "Greff", 209); 
 
    
 
    console.log(person.fullDetail());

(͡° ͜ʖ ͡°)

Answer 4

如果你在ES6，你可以使用新的类语法像

class ExampleBaseClass { 
    // Do things here... 
} 

class ExampleClass extends ExampleBaseClass { 
    // Do other things here... 
    // You may use methods from ExampleBaseClass here. 
} 

参见：https://www.sitepoint.com/understanding-ecmascript-6-class-inheritance/