深浅拷贝

1.引用传递是浅拷贝,传递的是地址

　　例如obj2的改变，obj1也会改变

 1  var obj={
 2         name:"admin"
 3     }
 4     var obj2=obj
 5     console.log(obj)    //{name: "admin"}
 6     console.log(obj2)   //{name: "admin"}
 7 　　
 8     obj2.name="root"
 9     console.log(obj)    //{name: "root"}
10     console.log(obj2)   //{name: "root"}

2深拷贝

　　2.1 深拷贝1:遍历对象读取每个键值对，逐个复制，但是后面会有缺点

 2     var obj={
 3             name:"admin"
 4         }
 5     var obj2={};
 6     for(var i in obj){
 7         obj2[i]=obj[i]
 8     }
 9     console.log(obj)    //{name: "root"}
10     console.log(obj2)   //{name: "root"}
11 
12     obj2.name="root";
13     console.log(obj)    //{name: "root"}
14     console.log(obj2)   //{name: "root"}
15 
16     缺点
17     var obj={
18         name:{
19             name1:"admin"
20         }
21     }
22     var obj2={};
23     for(var i in obj){
24         obj2[i]=obj[i]
25     }
26     console.log(obj)    //name: {name: "admin"}
27     console.log(obj2)   //name: {name: "admin"}
28 
29     obj2.name.name1="root"
30     console.log(obj)    //name: {name1: "root"}
31     console.log(obj2)   //name: {name1: "root"}
32     此时会把obj内的属性值也会改变

　　2.2 深拷贝2：利用字符的值传递，将对象转成字符再转回来

 1 var obj = {
 2         name:{
 3             name1:{
 4                 name2:"admin"
 5             }
 6         }
 7     }
 8     // JSON.parses是字符转对象，JSON.stringify是对象转字符
 9     var obj2=JSON.parse(JSON.stringify(obj));
10     console.log(obj)    //obj
11     console.log(obj2)   //obj
12     obj2.name.name1.name2="root";
13     console.log(obj)    //name:"root"
14     console.log(obj2)   //name:"root"

　　2.3深拷贝3：利用Object.create()实现继承

 1 var obj={
 2         name:"admin"
 3         
 4     }
 5     var obj2=Object.create(obj);
 6     console.log(obj)    //{name: "admin"}
 7     console.log(obj2)   //{}
 8 
 9     obj2.name="root"
10     console.log(obj.name)   //admin
11     console.log(obj2.name)  //root
12     obj2.__proto__.name = "root"
13     console.log(obj.name)   //root
14     console.log(obj2.name)  //root

// 相当于继承了原型，obj是obj2的父级，修改obj2不会影响obj，除非在obj2上修改原型