<script type="text/javascript">

//继承第一种方式：对象冒充

function Parent(username) //父类对象
{
    this.username = username; //下面的代码最关键的部分就是将子对象的this传递给了父对象

    this.sayHello = function()
    {
        alert(this.username);
    }
}

function Child(username, password) //子类对象
{
    //下面三行代码是最关键的代码
    this.method = Parent; //定义method属性，指向Parent，即指向了上面的构造函数
    this.method(username);//把username传递过去，调用构造函数，此时Parent函数体中的this即当前的Child对象
    delete this.method; //删掉method属性，因为Child已经具备了Parent的属性和方法

    //下面可以增加一些子类特有的属性和方法
    this.password = password;

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

//生成这两个类的对象
var parent = new Parent("zhangsan");
var child = new Child("lisi", "1234");

parent.sayHello();

child.sayHello();
child.sayWorld();

</script>

<script type="text/javascript">

//call方法方式,Function对象中的方法

function test(str, str2)
{
    alert(this.name + ", " + str + ", " + str2);
}

var object = new Object();
object.name = "zhangsan";

//test.call相当于调用了test函数
test.call(object, "shengsiyuan", "hello"); //将object赋给了this
//第一个参数赋给this，后面的参数逐次赋给方法参数

</script>

<script type="text/javascript">

//使用call方式实现对象的继承

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

    this.sayHello = function()
    {
        alert(this.username);
    }
}

function Child(username, password)
{
    Parent.call(this, username);//这样语句很关键，等价于对象冒充中的三行语句
    //执行之后子类就具有了基类的属性和方法

    //子对象的新增属性和方法
    this.password = password;

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

var parent = new Parent("zhangsan");

var child = new Child("lisi", "123");

parent.sayHello();

child.sayHello();
child.sayWorld();


</script>

<script type="text/javascript">

//使用apply方法实现对象继承

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

    this.sayHello = function()
    {
        alert(this.username);
    }
}

function Child(username, password)
{
    Parent.apply(this, new Array(username));//apply方法方式实现继承，后面的参数以数组的形式传入

    this.password = password;

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


var parent = new Parent("zhangsan");
var child = new Child("lisi", "123");

parent.sayHello();

child.sayHello();
child.sayWorld();



</script>

<script type="text/javascript">

//使用原型链（prototype chain）方式实现对象继承

function Parent()
{

}

Parent.prototype.hello = "hello";
Parent.prototype.sayHello = function()
{
    alert(this.hello);
}

function Child()
{

}

Child.prototype = new Parent();//子类具有父类的属性和方法
//扩展属性
Child.prototype.world = "world";
Child.prototype.sayWorld = function()
{
    alert(this.world);
}

var child = new Child();

child.sayHello();
child.sayWorld();


</script>

<script type="text/javascript">

//使用混合方式实现对象继承(推荐)
//父对象
function Parent(hello)
{
    this.hello = hello;
}

Parent.prototype.sayHello = function()
{
    alert(this.hello);
}
//子对象
function Child(hello, world)
{
    Parent.call(this, hello);//通过call实现属性的继承

    this.world = world;//新增加的属性
}

Child.prototype = new Parent();//通过原型链实现方法的继承

Child.prototype.sayWorld = function()
{
    alert(this.world);
}

var child = new Child("hello", "world");

child.sayHello();
child.sayWorld();

</script>

<script type="text/javascript">

function Shape(edge)
{
    this.edge = edge;//属性，多少条边，通过构造函数的方式定义
}

Shape.prototype.getArea = function()//通过原型的方式来定义方法
{
    return -1;//基类返回一个没有意义的值
}

Shape.prototype.getEdge = function()
{
    return this.edge;
}

//定义子对象Triangle
function Triangle(bottom, height)
{
    Shape.call(this, 3);

    //Triangle的属性
    this.bottom = bottom;
    this.height = height;
}

Triangle.prototype = new Shape();//继承Shaple中的所有方法

Triangle.prototype.getArea = function()//重写方法
{
    return 0.5 * this.bottom * this.height;
}

var triangle = new Triangle(10, 4);

//alert(triangle.getEdge());
//alert(triangle.getArea());

//另一个子类：四边形
function Rectangle(bottom, height)
{
    Shape.call(this, 4);

    this.bottom = bottom;
    this.height = height;
}

Rectangle.prototype = new Shape();//通过原型继承父类的所有方法

Rectangle.prototype.getArea = function()//覆写方法
{
    return this.bottom * this.height;
}


var rectangle = new Rectangle(20, 40);

alert(rectangle.getEdge());
alert(rectangle.getArea());

</script>