JavaScript面向對象

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JavaScript面向對象

JavaScript中創建對象的方式

普通創建方式

<script type="text/javascript">
        var obj = new Object();
        //動態添加屬性
        obj.name="張三";
        obj.age = 15 ;
        obj["addr"]="銅鑼灣";
        obj.sayHello=function(){
            console.log("姓名："+this.name+",年齡"+this.age+",地址:"+this.addr);
        }
        obj.sayHello();
        //動態刪除屬性
        delete obj.addr;
        obj.sayHello();
</script>

在js中，屬性可以動態添加，也可以動態刪除

通過json格式創建對象

json的格式的表現形式

表現形式1

<script type="text/javascript">
        var obj={"name":"zhangsan","age":15,"addr":"南京"};
        console.log(obj.name,obj.age,obj.addr);
        console.log(typeof obj);
 </script>

表現形式2

注意：value的取值可以是以下內容

對于以上的結構，那么json的變種就非常豐富

案例1:

var obj=["張三",15,true,
                {
                    "fatherName":"張無忌",
                    "motherName":"無忌張", 
                    children:["張飛","張亮","張靚穎"]
                }
        ];
alert(typeof obj)
alert(obj[0]);
alert(obj[3]["children"])

案例2：

 var obj3= {
            "name":"zhangsan",
            "age":15,
            children:[
                {
                  name:"張一",
                  age:1
                },
                {
                    name:"lisi",
                    age:10
                },
                {
                    name:"wangwu",
                    age:12
                }
            ],
            sayInfo:function(){
                console.log(this.name,this.age);
            }
 };
obj3.sayInfo();
for(var i = 0 ;i<obj3.children.length;i++) {
  console.log(obj3.children[i].name,obj3.children[i].age)
}   

工廠方法創建對象

function createObject(name,age){
            var obj = new Object();
            obj.name = name ;
            obj.age = age
            obj.sayHello=sayHello;
            return obj ;
 }
var sayHello=function(){
    console.log(this.name,this.age);
}
var obj1 = createObject("張三",12);
obj1.sayHello();
var obj2 = createObject("李四",20);
obj2.sayHello();

構造函數創建的對象

<script type="text/javascript">
function Person(name,age){
  this.name = name ;
  this.age  =age ;
  this.sayHello= sayHello;
}
function sayHello(){
    console.log(this.name,this.age)
}
//隱藏了一個創建的對象的過程
var p1 =new Person("張三",12);
var p2 = new Person("李四",15);
p1.sayHello();
p2.sayHello();
</script>

采用原型創建對象

<script type="text/javascript">
        function Person(name,age){
            this.name = name ;
            this.age = age ;
        }
        Person.prototype.sayHello = function(){
            console.log(this.name,this.age);
        }
        var p1  = new Person("張三",15);
        var p2  = new Person("lisi",16);
        p1.sayHello();
        p2.sayHello();
</script>

使用原型+構造函數方式來定義對象，對象之間的屬性互不干擾，各個對象間共享同一個方法

優化上面的案例

<script type="text/javascript">
        function Person(name,age) {
            this.name = name ;
            this.age = age ;
            //第一次創建對象的，通過參數給原型上增加一個共享的方法
            if(typeof Person.prototype.flag==="undefined") {
                alert("invoked...");
                Person.prototype.sayInfo = function(){
                    console.log(this.name,this.age)
                };
                Person.prototype.flag = true ;
            }
        }
        var  p1 = new Person("zhangsan",12);
        var  p2 = new Person("lisi",15);

        p1.sayInfo();
        p2.sayInfo()
</script>

JavaScript中的繼承機制

對象冒充

function Parent(name,age) {
  this.name= name ;
  this.age = age ;
  this.sayInfo = function(){
    console.log(this.name,this.age) ;
  }
 }
function Son(name,age,addr) {
  this.method=Parent;
  this.method(name,age);
  this.addr = addr ;
  //將自定義的method方法刪除掉
  delete this.method;
  this.sayInfo=function(){
    console.log(this.name,this.age,this.addr) ;
  }
}

apply和call方法

function Parent(name,age) {
  this.name = name ;
  this.age = age ;
  this.sayInfo=function(){
    console.log(this.name,this.age);
  };
}

function Son(name,age,addr) {
  //call接受的離散的值,apply的參數為數組
  //Parent.call(this,name,age);
  Parent.apply(this,new Array(name,age));
  this.addr = addr ;
  this.sayInfo=function(){
    console.log(this.name,this.age,this.addr);
  }
}
var s = new Son("張三",15,"北京");
console.log(s)
s.sayInfo();

原型混合方式

<script type="text/javascript">
        //apply|call+原型混合方式
        function Parent(name,age) {
            this.name = name ;
            this.age = age ;

        }
        Parent.prototype.sayInfo=function(){
            console.log(this.name,this.age);
        }

        function Son(name,age,addr) {
            //只能做屬性復制
            Parent.apply(this,new Array(name,age));
            this.addr = addr ;
        }
        //拿原型中方法
        Son.prototype=new Parent();
        var s = new Son("zhangsan",12);
        console.log(s)
<script>