1.浅拷贝

既传值也传址

       var arr  =[1,2,3];
       var b = arr;
       b.push(4);
       console.log(arr);

2.深拷贝

只传值

        var  arr = [1,2,3];
        var b = arr.slice(0,);

         arr.forEach(item=>{
             b.push(item);
         })

        var arr = [{name:"cheng"},{name:"zhang"},{name:"li"}];
        var res = [...arr];
        res[0].name="huang";
        res.push({name:"vue"});
        console.log(arr);

var arr = [{name:"cheng"},{name:"zhang"},{name:"li"}];

var arr = [{name:"cheng"},{name:"zhang"},{name:"li"}]; 
var res = [...arr];

遇到复杂类型(array+object)如何实现深拷贝

var obj = {name:{name:"cheng"}};
        function deepClone(obj){
            /* 1.能够识别数组和对象了 */
                let result;
                if(typeof obj=="number" || obj == null || typeof obj=="boolean"||typeof obj=="string"){
                    return obj;
                }
                if(obj instanceof Array || typeof obj == "object"){
                    /* 2.对拷贝的值作初始值得设定 */
                    if(obj instanceof Array){
                        result = [];
                    }else if(typeof obj =="object"){
                        result = {};
                    }
                    /* 3.需要将obj克隆到result中 */
                    for(let key in obj){
                        result[key] = deepClone(obj[key]);
                    }
                    return result;
                }
        }
        var res = deepClone(obj);
        console.log(res)

简单数据类型实现深拷贝

    1. {...obj}<br />        2. Object.assign()

        var obj = {name:"cheng",age:18};
        // var a = {...obj};
        var a = Object.assign({},obj);
        obj.id= 100;
        console.log(a);

3.vue深拷贝

        name:<input type="text" v-model="newItem.name">
        id:<input type="text" v-model="newItem.id">
        <button @click="doAdd">添加</button>
        <div v-for="item of arr">
            {{item.name}}
        </div>

        new Vue({
            el:"#app",
            data:{
                newItem:{
                    name:"",
                    id:""
                },
                arr:[
                    {name:"vue",id:1001},
                    {name:"html",id:1001},
                    {name:"css",id:1001}
                ]
            },
            methods:{
                doAdd(){
                    var res = {...this.newItem} 
                    this.arr.push(res)
                }
            }
        })