ttitfly的笔记

//第一种方式,冒充对象的方式.(利用js里的每一个方法名都是一个Function对象)
function Parent(username){
	this.username = username;
	this.say = function(){
		alert(this.username);
	}
}

function Child(username,password){
	
	this.temp = Parent;//temp指向Parent所指向的地方 。 利用js里的每一个方法名都是一个Function对象,指向一个方法。
	this.temp(username);//初始化方法里的内容
	delete this.temp;//temp没有用了。可以直接删除掉.this不可以丢了
	
	
	//Parent(username);//这样写表面看起来是正确的，其实是错误的。因为只有new出来的对象才有this,所以调用Parent里的this就没有值了
	
	
	this.password = password;
	this.hello = function(){
		alert(this.password);
	}
}

var parent = new Parent("zhangsan");
parent.say();//zhangsan

var child = new Child("lisi","123456");
child.say();//lisi
child.hello();//123456

//call()函数是Function对象的一个函数
//具体用法如 
function test(str){
	alert(this.username + ","  + str);
}

var o = new Object();
o.username = "zhangsan";
test.call(o,"123456");//zhangsan,123456 .因为每个Function 对象都有一个call()方法，而函数名就是一个Function对象.call()函数的第一个参数是test函数里的this.

function Parent(username){
	this.username = username;
	this.say = function(){
		alert(this.username);
	}
}
function Child(username,password){
	Parent.call(this,username);
	this.password = password;
	this.hello = function(){
		alert(this.password);
	}
}
var parent = new Parent("zhangsan");
parent.say();//zhangsan

var child = new Child("lisi","123456");
child.say();//lisi
child.hello();//123456

//第三种实现方式:apply()函数方式，apply()和call()是一样的，只不过参数传递不同而已,apply的参数为数组
//所以继承可以这样实现

function Parent(username){
	this.username = username;
	this.say = function(){
		alert(this.username);
	}
}
function Child(username,password){
	Parent.apply(this,new Array(username));
	this.password = password;
	this.hello = function(){
		alert(this.password);
	}
}
var parent = new Parent("zhangsan");
parent.say();//zhangsan

var child = new Child("lisi","123456");
child.say();//lisi
child.hello();//123456

//原型链实现继承
function Parent(){
}
Parent.prototype.hello = "hello";
Parent.prototype.sayHello = function(){
	alert(this.hello);
}

function Child (){
}
Child.prototype = new Parent();//关键

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

var child = new Child();
child.sayHello();
child.sayWorld();

//混合模式实现继承
function Parent(hello){
	this.hello = hello;
}
Parent.prototype.sayHello = function(){
	alert(this.hello);
}

function Child(hello,world){
	this.world = world;
	Parent.call(this,hello);//关键

}
Child.prototype = new Parent(); //关键
Child.prototype.sayWorld = function(){
	alert(this.world);
}

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