JavaScript对象原型

所有JavaScript对象都从原型继承属性和方法。

<!DOCTYPE html><html><meta charset="utf-8"><title>js</title><body><h3>JavaScript 对象</h3><p id="demo"></p><script> 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;</script></body></html>

我们还了解到，您无法向现有对象构造函数添加新属性：

<!DOCTYPE html><html><meta charset="utf-8"><title>JavaScript对象</title><body><h3>JavaScript对象</h3><p>您无法向构造函数添加新属性。</p><p id="demo"></p><script> 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;</script></body></html>

要向构造函数添加新属性，必须将其添加到构造函数：

<!DOCTYPE html><html><meta charset="utf-8"><title>JavaScript对象</title><body><h3> JavaScript对象</h3><p id="demo"></p><script> 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;</script></body></html>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.prototypeArray 对象继承自 Array.prototypePerson 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：

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：

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;};

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