JavaScript学习总结(九)——Javascript面向(基于)对象编程

一、澄清概念

　　1.JS中"基于对象=面向对象"

　　2.JS中没有类(Class)，但是它取了一个新的名字叫“原型对象”，因此"类=原型对象"

二、类(原型对象)和对象(实例)的区别与联系

　　1.类(原型对象)是抽象，是概念的，代表一类事物。

　　2.对象是具体的，实际的，代表一个具体的事物。

　　3.类(原型对象)是对象实例的模板，对象实例是类的一个个体。

三、抽象的定义

　　在定义一个类时，实际上就是把一类事物的共有属性和行为提取出来，形成一个物理模型(模板)，这种研究问题的方法称为抽象。

四、JavaScript面向对象三大特征

　　4.1.封装

　　封装就是把抽象出来的属性和对属性的操作封装在一起，属性被保护在内部，程序的其它部分只有通过被授权的操作(函数)，才能对属性进行操作！

封装的范例：

 1 <script type="text/javascript">

 2     /*定义一个Person类*/

 3     function Person(_name,_age,_salary){

 4         //Person类的公开属性，类的公开属性的定义方式是：”this.属性名“

 5         this.Name=_name;

 6         //Person类的私有属性，类的私有属性的定义方式是：”var 属性名“

 7         var Age=_age;

 8         var Salary=_salary;

 9

10         //定义Person类的公开方法(特权方法)，类的公开方法的定义方式是：”this.functionName=function(){.....}“

11         this.Show=function(){

12             alert("Age="+Age+"\t"+"Salary="+Salary);//在公开方法里面访问类的私有属性是允许的

13         }

14         /*

15         定义Person类的私有方法(内部方法)，

16         类的私有方法的定义方式是：”function functionName(){.....}“，

17         或者 var functionName=function(){....}

18         */

19         function privateFn(){

20             alert("我是Person类的私有函数privateFn");

21         }

22

23         var privateFn2=function(){

24             alert("我是Person类的私有函数privateFn2");

25         }

26     }

27     /*通过prototype给可以类的所有对象添加公共(public)方法，

28     但是这种方式定义的方法不能去访问类的私有属性和私有方法*/

29     Person.prototype.Fn=function(){

30         alert("访问公共属性this.Name="+this.Name);//访问公共属性，OK的

31         //alert("访问私有属性Aag="+Age);//访问私有属性，这里会报错“Age未定义”

32         //privateFn();//调用私有方法，这里会报错“缺少对象”

33

34     }

35

36     var p1 = new Person("孤傲苍狼",24,2300);

37     alert("p1.Name="+p1.Name);//访问公有属性，这是可以正常访问的

38     alert("p1.Age="+p1.Age+"\t"+"p1.Salary="+p1.Salary);//不能使用类的对象去直接访问类私有属性，这是访问不了的，结果都是undefined

39     p1.Show();//调用类的公共函数，这次允许的

40     p1.Fn();//调用类的公共函数，这次允许的

41     //alert("p1.privateFn()："+p1.privateFn()+"&nbsp;p1.privateFn2()："+p1.privateFn2());//不能使用类的对象去调用类的私有方法，这里会报错”对象不支持此属性或者方法“

42   </script>

　　4.2.继承

继承范例：

 1 <script type="text/javascript">

 2     /*定义Stu类*/

 3     function Stu(name,age){

 4         this.Name=name;

 5         this.Age=age;

 6         this.Show=function(){

 7             window.alert("我的名字是："+this.Name+"，今年："+this.Age);

 8         }

 9         this.SayHello = function(){

10             window.alert("Hello，"+this.Name);

11         }

12     }

13

14     /*定义MidStu类*/

15     function MidStu(name,age){

16         this.stu=Stu;//MidStu类继承Stu类

17         this.stu(name,age);//JS中实际上是通过对象冒充来实现继承的，这句话不能少，因为JS是动态语言，如果不执行，则不能实现继承效果

18         /*

19         从父类继承下来的公共方法，可以根据实际情况选择重写

20         */

21         //在子类MidStu中重写父类Stu的Show方法

22         /*this.Show=function(){

23             alert("MidStu.Show()");

24         }*/

25         //在子类MidStu中重写父类Stu的SayHello方法

26         this.SayHello=function(){

27             alert("你好，"+this.Name);

28         }

29

30     }

31

32     var midStu = new MidStu("孤傲苍狼",24);//创建一个MidStu类实例对象

33     alert("访问继承下来的属性Name和Age，midStu.Name="+midStu.Name+"，midStu.Name="+midStu.Age);//访问继承下来的属性

34     midStu.Show();//调用从父类Stu继承下来的Show方法

35     midStu.SayHello();//调用从父类Stu继承下来的SayHello方法，SayHello()在子类中进行了重写，这里调用的是重写过后的SayHello()方法

36   </script>

运行结果：

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" 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" 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" alt="" />

4.3.多态

　　所谓多态，就是指一个引用在不同情况下的多种状态，在Java中多态是指通过指向父类的引用，来调用不同子类中实现的方法。

　　JS实际上是无态的，是一种动态语言，一个变量的类型是在运行过程中由JS引擎决定的，所以说，JS天然支持多态。

五、JavaScript自定义类(原型对象)的方式

　　5.1.工厂方法——使用new Object创建对象并添加相关属性

 1     //通过Object直接创建对象

 2     //var p1 = new Object();//创建一个Object对象

 3     var p1 = {};//创建一个Object对象，简写

 4     //动态增加属性、方法

 5     p1.Name = "孤傲苍狼";

 6     p1.Age = 24;

 7     p1.SayHello = function() { alert("hello，"+p1.Name); };

 8     p1.SayHello();

 9     for(var propertyName in p1) {//对象的成员都是对象的key

10         alert(propertyName);

11     }

　　5.2.使用构造函数来定义类(原型对象)

基本语法：

 1 function 类名(){

 2      this.属性名;//公共属性

 3      var 属性名;//私有属性

 4      /*凡是定义类的公共属性和公共方法都要使用this*/

 5      //定义类的公共函数

 6      this.函数名=function(){

 7

 8      }

 9      //定义类的私有函数

10      function 函数名(){

11

12      }

13 }

范例：

 1 /*定义一个猫类，这种就是使用构造函数来定义类(原型对象)*/

 2     function Cat(){

 3         this.Name="catName";//public属性

 4         this.Age;//public属性

 5         this.Color;//public属性

 6         var weight=2;//private属性，只能在Cat类内部使用，Cat类的对象无法访问这个私有属性

 7         //public方法

 8         this.publicFunction = function(){

 9             alert(weight);

10             alert("猫叫...");

11         }

12         //private方法，只能在Cat类内部使用，Cat类的对象无法访问这个私有方法

13         var privateFunction = function(){

14             alert("私有方法");

15         }

16

17

18     }

19     //如果这样用，那么就当成函数来使用

20     Cat();

21     //如果这样用，那么就当成类来使用

22     var cat1 = new Cat();

23     //cat1就是一个对象(实例)

24     alert(cat1.Name);//访问公共属性，弹出默认值catName

25     cat1.Name="TomCat";//访问公共属性

26     cat1.Age=3;//访问公共属性

27     cat1.Color="白色";//访问公共属性

28     alert(cat1.weight);//访问私有属性，无法访问，弹出undefined

29     alert(cat1.Name+"\t"+cat1.Age+"\t"+cat1.Color);//访问对象的属性方式1：对象名.属性名

30     alert(cat1["Name"]+"\t"+cat1["Age"]+"\t"+cat1["Color"]);//访问对象的属性方式2：对象名["属性名"]

31     cat1.publicFunction();//调用public方法

32     cat1.privateFunction();//调用private方法，报错：对象不支持此属性或方法

33     for(var property in cat1){

34         document.writeln(property+"\t");

35     }

JS中一切都是对象，类(原型对象)其实也是对象，它实际上是Function类的一个实例

 1 document.write("<pre>");

 2     function Person(){

 3

 4     }

 5     /*Person.constructor得到的Person类的构造函数如下：

 6         function Function() {

 7             [native code]

 8         }

 9     */

10     document.writeln("Person.constructor："+Person.constructor);//Person类的构造函数

11     document.writeln("Person："+Person);

12     var p1 = new Person();

13     document.writeln("p1.constructor："+p1.constructor);//”p1.constructor“是得到p1实例的构造函数

14     //如何判断某个对象是不是某个类型，采用如下两种方式

15     if(p1 instanceof Person){

16         document.writeln("p1 is Person ok1");

17     }

18     if(p1.constructor==Person){

19         document.writeln("p1 is Person ok2");

20     }

21

22     var num1=123;

23     document.writeln("num1.constructor："+num1.constructor);

24

25     var str1="abc";

26     document.writeln("str1.constructor："+str1.constructor);

27     document.write("</pre>")

运行结果：

Person.constructor：

function Function() {

    [native code]

}

Person：function Person(){

	}

p1.constructor：function Person(){

	}

p1 is Person ok1

p1 is Person ok2

num1.constructor：

function Number() {

    [native code]

}

str1.constructor：

function String() {

    [native code]

}