function Person(){ } Person.prototype.name = "Nicholas"; Person.prototype.age = 29; Person.prototype.job = "Software Engineer"; Person.prototype.sayName = function(){ alert(this.name); }; var person1 = new Person(); var person2 = new Person(); person1.name = "Greg"; alert(person1.name); //"Greg" ?from instance alert(person2.name); //"Nicholas" ?from prototype delete person1.name; alert(person1.name); //"Nicholas" - from the prototype
6、hasOwnProperty方法
这个方法可以检测一个属性是否存在于实例中，还是存在于原型中！hasOwnProperty是从Object继承来的，只要给定属性存在于对象实例中，才会返回true.
function Person(){ } Person.prototype.name = "Nicholas"; Person.prototype.age = 29; Person.prototype.job = "Software Engineer"; Person.prototype.sayName = function(){ alert(this.name); }; var person1 = new Person(); var person2 = new Person(); alert(person1.hasOwnProperty("name")); //false alert("name" in person1); //true person1.name = "Greg"; alert(person1.name); //"Greg" ?from instance alert(person1.hasOwnProperty("name")); //true alert("name" in person1); //true alert(person2.name); //"Nicholas" ?from prototype alert(person2.hasOwnProperty("name")); //false alert("name" in person2); //true delete person1.name; alert(person1.name); //"Nicholas" - from the prototype alert(person1.hasOwnProperty("name")); //false alert("name" in person1); //true
7、Object.keys() 可枚举属性方法
这个方法接收一个对象作为参数，返回一个包含所有可枚举属性的字符串数组
function Person(){ } Person.prototype.name = "Nicholas"; Person.prototype.age = 29; Person.prototype.job = "Software Engineer"; Person.prototype.sayName = function(){ alert(this.name); }; var keys = Object.keys(Person.prototype); alert(keys); //"name,age,job,sayName" 如果想得到所有实例的属性，无论它是否可以枚举都可以使用这个方法来获取 function Person(){ } Person.prototype.name = "Nicholas"; Person.prototype.age = 29; Person.prototype.job = "Software Engineer"; Person.prototype.sayName = function(){ alert(this.name); }; var keys = Object.getOwnPropertyNames(Person.prototype); alert(keys); //"constructor,name,age,job,sayName"
此方法高版本浏览器才支持
8、简单的原型写法
function Person(){ } Person.prototype = { name : "Nicholas", age : 29, job: "Software Engineer", sayName : function () { alert(this.name); } }; var friend = new Person(); alert(friend instanceof Object); //true alert(friend instanceof Person); //true alert(friend.constructor == Person); //false alert(friend.constructor == Object); //true
重写了原型就等于将默认的原型方法覆盖，那么同样的构造方法也会被重写，重写的构造方法指向了Object对象！而不是原来的对象Person
如果还是想指向之前的构造方法，可以显示的指定
function Person(){ } Person.prototype = { constructor : Person, name : "Nicholas", age : 29, job: "Software Engineer", sayName : function () { alert(this.name); } }; var friend = new Person(); alert(friend instanceof Object); //true alert(friend instanceof Person); //true alert(friend.constructor == Person); //true alert(friend.constructor == Object); //false
9、原型方法的动态添加
function Person(){ } Person.prototype = { constructor: Person, name : "Nicholas", age : 29, job : "Software Engineer", sayName : function () { alert(this.name); } }; var friend = new Person(); Person.prototype.sayHi = function(){ alert("hi"); }; friend.sayHi(); //"hi" ?works!
10、原生对象的原型方法
alert(typeof Array.prototype.sort); //"function" alert(typeof String.prototype.substring); //"function" String.prototype.startsWith = function (text) {//修改原生对象的原型方法 return this.indexOf(text) == 0; }; var msg = "Hello world!"; alert(msg.startsWith("Hello")); //true
11、组合使用构造函数和原型模式创建对象
//构造函数模式 function Person(name, age, job){ this.name = name; this.age = age; this.job = job; this.friends = ["Shelby", "Court"]; } //原型模式 Person.prototype = { constructor: Person, sayName : function () { alert(this.name); } }; var person1 = new Person("Nicholas", 29, "Software Engineer"); var person2 = new Person("Greg", 27, "Doctor"); person1.friends.push("Van"); alert(person1.friends); //"Shelby,Court,Van" alert(person2.friends); //"Shelby,Court" alert(person1.friends === person2.friends); //false alert(person1.sayName === person2.sayName); //true
12、动态原型模式