数据赋值拷贝

1,值得赋值是独立的

num1=12;

num1=num2

将存储值赋值一份存储.

2,

var age=22;

age2=age;

age=24

console.log(age);

age2依旧是22

引用类型的赋值共享数据

指向同一片内存

3,对象的赋值

var p={

    name:"shizi",

    age:22,

}

p1=p;

console.log(p.name,p.age);

console.log(p1.name,p1.age);

console.log("------------------------");

p.name="maotai";

p.age=24;

console.log(p.name,p.age);

console.log(p1.name,p1.age);

值类型赋值--函数形参&实参

var num = 10;

function foo(num){

    num=100;

    console.log(num);

}

console.log(num);

#10

var num = 10;

function foo(num1){

    //实参: 调用时传递的参数

    //形参: 定义时传递的参数

    num1=100;

    console.log(num1);

}

foo(num);

console.log(num);

# 10 100 10

var num = 10;

function foo(num1){

    //实参: 调用时传递的参数

    //形参: 定义时传递的参数

    //var num1=num;

    num1=100;

    console.log(num1);

}

foo(num);

console.log(num);

# 10 100 10

引用类型赋值

1

var obj={

    name:"宅男"

}

function jinhua(param){

    param.name="高富帅";

}

jinhua(obj);

console.log(obj.name);

#高富刷

2

var obj={

    name:"宅男"

}

function jinhua(param){

    param.name="高富帅";

    //重新开辟内存,param重新指向一片mem

    param={

        name: "腐女"

    }

    param.name="宅男";

}

jinhua(obj);

console.log(obj.name);

#宅男

对象的动态性

动态添加属性和方法

p={

    name:"刘德华",

    age:22

}

//添加属性方式1

p.gender="male";

//添加属性方式2

p["salary"]=2000;

//添加对象类型属性

p.foo=function(){console.log("sing");}

//访问属性方式1

console.log(p.foo());

console.log(p.salary);

//访问属性方式2

console.log(p["name"];

p={

    name:"刘德华",

    age:22

}

p["salary"]=2000;  //是字符串

console.log(p.salary);

p={

    name:"刘德华",

    age:22

}

p[0]=2000; //隐式将0转换为字符串

//console.log(p.0); //发现这种方式访问报错

console.log(p["0"]); //这种方式正常访问

以下等价

p={

    name:"刘德华",

    age:22

}

p[{}]="shizi";

console.log(p);

p={

    name:"刘德华",

    age:22

}

p["[object Object]"]="shizi";

console.log(p);

探究

a={}

console.log(a.toString());

#"[object Object]"