** JavaScript对象原型**
所有JavaScript对象都从原型继承属性和方法。
```javascript

function Person(first, last, age, eye) {
        this.firstName = first;
        this.lastName = last;
        this.age = age;
        this.eyeColor = eye;
    }

var myFather = new Person("John", "Doe", 50, "blue");
    var myMother = new Person("Sally", "Rally", 48, "green");

document.getElementById("demo").innerHTML =
        "My father is " + myFather.age + ". My mother is " + myMother.age;
```
我们还了解到，您无法向现有对象构造函数添加新属性：
```javascript
    function Person(first, last, age, eye) {
        this.firstName = first;
        this.lastName = last;
        this.age = age;
        this.eyeColor = eye;
    }

Person.nationality = "English";

var myFather = new Person("John", "Doe", 50, "blue");
    var myMother = new Person("Sally", "Rally", 48, "green");

document.getElementById("demo").innerHTML =
        "The nationality of my father is " + myFather.nationality;
```

要向构造函数添加新属性，必须将其添加到构造函数：
```javascript
    function Person(first, last, age, eye) {
        this.firstName = first;
        this.lastName = last;
        this.age = age;
        this.eyeColor = eye;
        this.nationality = "English";
    }

var myFather = new Person("John", "Doe", 50, "blue");
    var myMother = new Person("Sally", "Rally", 48, "green");

document.getElementById("demo").innerHTML =
        "我父亲的国籍是 " + myFather.nationality + ". 我母亲的国籍是： " + myMother.nationality;
```

**原型继承**
    所有JavaScript对象都从原型继承属性和方法：
    Object.prototype位于原型继承链的顶部：Date对象，Array对象和Person对象继承自Object.prototype。
    *   Date 对象继承自 Date.prototype
    *   Array 对象继承自 Array.prototype
    *   Person 对象继承自 Person.prototype

**向对象添加属性和方法**

有时，您希望向给定类型的所有现有对象添加新属性（或方法）。有时您想要向对象构造函数添加新属性（或方法）。

**使用**原型**属性**

JavaScript prototype属性允许您向对象构造函数添加新属性：

```javascript
function Person(first, last, age, eyecolor) {
  this.firstName = first;
  this.lastName = last;
  this.age = age;
  this.eyeColor = eyecolor;
}
Person.prototype.nationality = "English";

```

JavaScript prototype属性还允许您向对象构造函数添加新方法：

```javascript
function Person(first, last, age, eyecolor) {
  this.firstName = first;
  this.lastName = last;
  this.age = age;
  this.eyeColor = eyecolor;
}
Person.prototype.name = function() {
  return this.firstName + " " + this.lastName;
};

```

[更好的原型对象的文章](https://www.jc2182.com/javascript-obj-define/1642.html)

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JavaScript prototype原型用法

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