面向对象JS编程（一）——创建对象

1.普通模式

var person = new Object();

person.name = "Laughing";
person.age = 28;
person.job = "Software Engineer";

peron.sayName = function(){
    alert(this.name);
};

person.sayName();

缺点：创建多个对象时，会产生大量的重复代码。

2.工厂模式

function createPerson(name, age, job){
    var o = new Object();
    o.name = name;
    o.age = age;
    o.job = job;
    o.sayName = function(){
        alert(this.name);
    };
    return o;
}

var person1 = new Person("Laughing", 28, "Software Enginner");
var person2 = new Person("Greg", 27, "Doctor");

缺点：无法识别对象的类型。

3.构造函数模式

function Person(name, age, job){
    this.name = name;
    this.age = age;
    this.job = job;
    this.sayName = function(){
        alert(this.name);
    };
}

var person1 = new Person("Laughing", 28, "Software Enginner");
var person2 = new Person("Greg", 27, "Doctor");

优点：可以使用instanceof判断对象类型，即alert(person1 instanceof Person); //true

缺点：每个方法都需要在每个实例上重新创建一遍。

4.原型模式

function Person(){
}

Person.prototype.name = "Laughing";
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.sayName == person2.sayName); //true

缺点：对于包含引用类型值的属性，共享非常不合适。如：

function Person(){
}

//更简单的原型模式
Person.prototype = {
    constructor: Person, //重新指定constructor
    name : "Laughing",
    age : 29,
    job : "Software Engineer",
    friends : ["Shelby", "Court"],
    sayName : function(){
        alert(this.name);
    }
};

var person1 = new Person();
var person2 = new Person();

person1.friends.push("Van");

alert(person1.friends); //"Shelby, Court, Van"
alert(person2.friends); //"Shelby, Court, Van"　期望是 "Shelby, Court"

5.原型构造模式

function Person(name, age, job){
    this.name = name;
    this.age = age;
    this.job = job;
    this.friends = ["Shelby", "Court"];
}

Person.prototype = {
    constructor : Person,
    sayName : function(){
        alert(this.name);
    }
};

var person1 = new Person("Laughing", 28, "Software Engineer");
var person2 = new Person("Greg", 29, "Doctor");

person1.friends.push("Van");

alert(person1.friends); //"Shelby, Count, Van"
alert(person2.friends); //"Shelby, Count"