js定义对象的方法和继承的方法

定义对象的方法

基于已有对象扩充其对象和方法(只适合于临时的生成一个对象)：

var obj = new Object();
//两种增加对象属性的方法
obj.username = "user";
obj["password"] = 123;
//增加方法
obj.show  =function(username,password){
this.username = username;
this.password = password;
alert(this.username+":"+this.password);
}
//删除属性
delete obj.username;

2.开发最为常见的定义对象方式

var obj = {username:"root",password:123};
alert(obj.username+":"+obj.password);

有方法的：

var obj = {username:"root",password:54,
show :function(){
alert(this.username+":"+this.password);
}
};

obj.show();

3.工厂模式(无参)

function createObject(){
var obj = new Object();

obj.username = "root";
obj.password = 123;

obj.show = function(){
alert(this.username+":"+this.password);
};
return obj;
}

var obj1 = createObject();
obj1.username = "fate";
var obj2 = createObject();
obj1.show();
obj2.show();

4.工厂模式（带参数）

function createObject(username,password)
{
var obj = new Object();

obj.username = username;
obj.password = password;

obj.show = function()
{
alert(this.username +":"+ this.password);
};
return obj;
}

var obj = createObject("fate","1234");
obj.show();

让方法被多个对象共享：

function createObject(username,password)
{
var obj = new Object();

obj.username = username;
obj.password = password;
obj.show = show;

return obj;
}
//把方法创建到对象工厂外面，被多对象共享
var show = function()
{
alert(this.username +":"+ this.password);
};

var obj1 = createObject("小明","1234");
var obj2 = createObject("张三","4564");
obj1.show();
obj2.show();

5.构造函数方法

无参：

function Person(){
//在执行第一行代码前，js引擎会为我们生成一个对象
this.username = "小明";
this.password = "1564";

this.show = function(){
alert(this.username+":"+this.password);
}
//此处隐藏一个return语句，用于把生成的对象返回
}
//在这里new一个对象
var p = new Person();
p.show();

有参：

function Person(username,password){
//在执行第一行代码前，js引擎会为我们生成一个对象
this.username = username;
this.password = password;

this.show = function(){
alert(this.username+":"+this.password);
}
//此处隐藏一个return语句，用于把生成的对象返回
}
//在这里new一个对象
var p = new Person("小红","464641");
p.show();

6.原型（ prototype）方式

function Person(){

}
//用prototype添加对象的属性和方法
Person.prototype.username = "张三";
Person.prototype.password = "1389";

Person.prototype.show = function(){
alert(this.username+":"+this.password);
};
//new对象
var person1 =  new Person();
var person2 = new Person();
person1.username = "夏天";

person1.show();
person2.show();

prototype增加的属性为数组：

function Person(){

}
//用prototype添加对象的属性和方法
Person.prototype.username = new Array();
Person.prototype.password = "1389";

Person.prototype.show = function(){
alert(this.username+":"+this.password);
};
//new对象
var person1 =  new Person();
var person2 = new Person();
person1.username = "夏天";
person2.username = "林";
person1.password = "168";

person1.show();
person2.show();

缺点：：单纯使用原型方式创建对象，无法给对象传参数，只能通过创建对象后再去改变属性的值

7. 原型+构造函数方式（各个对象之间互不干扰，各个对象共享一个方法）

function Person(password){
this.username = new Array();
this.password = password;
}

Person.prototype.show = function(){
alert(this.username+":"+this.password);
};

var p1 = new Person("5644");
var p2 = new Person("111111");

p1.username.push("小白");
p2.username.push("小黑");

p1.show();
p2.show();

8.动态原型方式：在构造函数中通过标质量让所有对象共享一个方法，而每个对象拥有自己的属性。

function Person(){
this.username = "小白";
this.password = "156";
//做一个判断标志，让方法只产生一次
if(typeof Person.flag == "undefined"){//这里只要Person.flag不等于Undefined，其他的值都为true
Person.prototype.show = function(){
alert(this.username+":"+this.password);
};
Person.flag = true;
}
}

var p1 = new Person();
var p2 = new Person();
p1.username = "大白";
p1.show();
p2.show();

javacript继承的方法

对象冒充

//父对象
function Parent(username){
this.username = username;

this.show = function(){
alert(this.username);
};
}
//子对象
function Child(username,password){
//下面三行为关键代码
this.method = Parent;
this.method(username);
delete this.method;

//子类特有的属性和方法
this.password = password;
this.showInfo = function(){
alert(this.password);
};
}

var parent = new Parent("小红");
var child = new Child("小明","321345");

parent.show();
//子类能够调用父类的属性和方法
child.username ="大白";
child.show();
child.showInfo();

2.call的方法方式(父类引用在子类中调用call方法，第一个参数传代表子类的this，后面根据父类参数依次传)

//父类
function Parent(username){
this.username = username;

this.show = function(){
alert(this.username);
};
}
//子类
function Child(username,password){
//父类对象调用call方法，把代表子类的this传过去
Parent.call(this, username);

this.password = password;

this.showInfo = function(){
alert(this.password);
};
}

var parent = new Parent("小红");
var child = new Child("小白","15");

parent.show();
//子类继承父类的方法
child.show();
child.showInfo();

3.apply方法

//父类
function Parent(username,age){
this.username = username;
this.age = age;

this.show = function(){
alert(this.username);
};
}
//子类
function Child(username,password,age){//子类的参数要包含父类的所有参数
//父类对象调用apply方法，把代表子类的this传过去,后面父类对应的所有参数都依次添加到数组中
Parent.apply(this, new Array(username,age));

this.password = password;

this.showInfo = function(){
alert(this.password);
};
}

var parent = new Parent("小红");
var child = new Child("小白白","15");

parent.show();
//子类继承父类的方法
child.age = "24";
child.show();
child.showInfo();

4.原型链方式（无法给构造方法传参）

//父类
function Parent(){

}

Parent.prototype.username = "小白";
Parent.prototype.show = function(){
alert(this.username);
};
//子类
function Child(){

}
//关键代码，这样子类就拥有了父类用prototype添加的属性和方法，不是prototype添加的子类没有继承
Child.prototype  = new Parent();

Child.prototype.password = "484984";
Child.prototype.showInfo = function(){
alert(this.password);
};

var child = new Child();
//子类继承了父类的属性和方法
child.username = "小小";
child.show();
child.showInfo();

5.混合模式（推荐使用）

//父类
function Parent(username){
this.username = username;
}
//给父类添加方法
Parent.prototype.show = function(){
alert(this.username);
};
//让子类拥有了父类的username
function Child(username,password){
Parent.call(this,username);
this.password = password;
}
//让子类拥有了父类用prototype添加的show()方法
Child.prototype = new Parent();

Child.prototype.showInfo = function(){
alert(this.password);
};

var child = new Child("小白","748974854");

child.show();
child.showInfo();