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> <h2>JavaScript 对象</h2> <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> <h2>JavaScript对象</h2> <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> <h2> JavaScript对象</h2> <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.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：
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; };