javascript对象的遍历、内存分布和封装特性

javascript对象的遍历、内存分布和封装特性

一、javascript对象遍历

1.javascript属性访问

对象.属性
对象.[属性] //属性必须为字符串格式

    var bottle={};
    bottle.brand="统一鲜橙多";
    bottle.capacity="2L";
    bottle.store=function () {
        return "装橙汁";
    };
    document.write(bottle.brand);
    document.write(" ");
    document.write(bottle["brand"]);

输出 统一鲜橙多 统一鲜橙多

2.javascript属性遍历

    var bottle={};
    bottle.brand="统一鲜橙多";
    bottle.capacity="2L";
    bottle.store=function () {
        return "装橙汁";
    };
    for(var i in bottle){
       document.write(bottle[i]+" ");
    }

输出 统一鲜橙多 2L function () { return "装橙汁"; }

模拟数组

    function myArray() {
        var len=arguments.length;
        for (var i=0;i<len;i++){
            this[i]=arguments[i];
        }
    }
    var arr=new myArray(1,2,3,4);
    for(var i in arr){
        document.write(arr[i]+" ");
    }

输出 1 2 3 4

二、内存分布

对象内存模型

三、对象的特性-封装

把对象所有的组成部分组合起来，尽可能地隐藏对象的部分细节，使其受到保护。只保留有限的接口和外部发送联系。

3.1工厂函数

   function ComputerFactory(brand,color,size) {
        var computer={};
        computer.brand=brand;
        computer.color=color;
        computer.size=size;
        computer.movie=function () {
            return "看电影";
        };
        computer.blog=function(){
            return "写博客";
        };
        computer.game=function () {
            return "玩游戏"
        };
        return computer;
    }
    var cp1=new ComputerFactory("Dell","白色","25英寸");
    for (var i in cp1){
        document.write(cp1[i]+" ");
    }
    document.write("<br/>");
    var cp2=new ComputerFactory("Lenovo","黑色","20英寸");
    for (var i in cp2){
        document.write(cp2[i]+" ");
    }

输出

Dell 白色 25英寸 function () { return "看电影"; } function(){ return "写博客"; } function () { return "玩游戏" }
Lenovo 黑色 20英寸 function () { return "看电影"; } function(){ return "写博客"; } function () { return "玩游戏" }

3.2构造方法的形式

    function Computer(brand,color,size) {
        this.brand=brand;
        this.color=color;
        this.size=size;
        this.movie=function () {
            return "看电影";
        };
        this.blog=function(){
            return "写博客";
        };
        this.game=function () {
            return "玩游戏"
        };
    }
    var acer=new Computer("acer","红色","25英寸");
    for (var i in acer){
        document.write(acer[i]+" ");
    }

输出

acer 红色 25英寸 function () { return "看电影"; } function(){ return "写博客"; } function () { return "玩游戏" }

3.3prototype方法
函数也是一个对象，prototype是函数的一个属性，这个属性指向函数对象的原型。

    function Bottle(brand,capacity,liquidName){
        this.brand=brand;
        this.capacity=capacity;
        this.store=function () {
            return "装"+liquidName;
        }
    }
    Bottle.prototype.recycled=function () {
        return "被回收";
    };
    var tongyi=new Bottle("统一鲜橙多","2L","橙汁");
    document.write(tongyi.store());
    document.write("&nbsp");
    document.write(tongyi.recycled());
    delete tongyi.store;
    delete tongyi.recycled;
    document.write("<br/>");
    document.write(tongyi.recycled());
    document.write("&nbsp");
    document.write(tongyi.store());

输出

装橙汁 被回收
被回收

prototype方法形式不能共享对象

    function Woman(name,tall){
        this.name=name;
        this.tall=tall;
        this.giveBirth=function () {
            return "生育";
        };

    }
    Woman.prototype.walk=function () {
        return "走路";
    };
    Woman.prototype.nextGeneration={name:"后代名"};
    var zhangsan=new Woman("张三","175cm");
    zhangsan.nextGeneration.name="张小三";
    document.write(zhangsan.name+" ",zhangsan.tall+" "+zhangsan.giveBirth()+" "+zhangsan.nextGeneration.name+" "+zhangsan.walk());
    document.write("<br/>");
    var lisi=new Woman("李四","165cm");
    document.write(lisi.name+" ",lisi.tall+" "+lisi.giveBirth()+" "+lisi.nextGeneration.name+" "+lisi.walk());

输出

张三 175cm 生育 张小三 走路
李四 165cm 生育 张小三 走路

3.4混合方式

    function Woman(name,tall){
        this.name=name;
        this.tall=tall;
        this.giveBirth=function () {
            return "生育";
        };
        Woman.prototype.nextGeneration={name:"后代"};
    }
    Woman.prototype.walk=function () {
        return "走路";
    };
    var zhangsan=new Woman("张三","175cm");
    zhangsan.nextGeneration.name="张小三";
    document.write(zhangsan.name+" ",zhangsan.tall+" "+zhangsan.giveBirth()+" "+zhangsan.nextGeneration.name+" "+zhangsan.walk());
    document.write("<br/>");
    var lisi=new Woman("李四","165cm");
    document.write(lisi.name+" ",lisi.tall+" "+lisi.giveBirth()+" "+lisi.nextGeneration.name+" "+lisi.walk());

输出

张三 175cm 生育 张小三 走路
李四 165cm 生育 后代 走路

    function Woman(name,tall,nextGenerationName){
        this.name=name;
        this.tall=tall;
        this.giveBirth=function () {
            return "生育";
        };
        Woman.prototype.nextGeneration={name:nextGenerationName};
    }
    Woman.prototype.walk=function () {
        return "走路";
    };
    var zhangsan=new Woman("张三","175cm","张小三");
    document.write(zhangsan.name+" ",zhangsan.tall+" "+zhangsan.giveBirth()+" "+zhangsan.nextGeneration.name+" "+zhangsan.walk());
    document.write("<br/>");
    var lisi=new Woman("李四","165cm","李小四");
    document.write(lisi.name+" ",lisi.tall+" "+lisi.giveBirth()+" "+lisi.nextGeneration.name+" "+lisi.walk());

输出

张三 175cm 生育 张小三 走路
李四 165cm 生育 李小四 走路