Set，拷贝

Set

//set特点：不重复，不是一个有序列的集合
var arr = [1,2,3,1]
var s = new Set([...arr])//数组去重
s.add(4)//添加数据
s.clear()//清空数据
s.delete(2)//删除2  ------shift，pop,splice(index,howmany)
s.forEach((item)=>{})//遍历数组
console.log(s.has(3));//true
console.log(s.entries());//参赛作品  SetIterator {1 => 1, 3 => 3, 4 => 4}

深拷贝浅拷贝

//vue中常用
//应用：在复杂类型（Array,Object)的赋值运算
//浅拷贝：既传值也传址 (栈，堆)
 var arr = [1,2,3];
 var b = arr;
 b.push(4);
 console.log(arr);
//深拷贝：只传值
arr=[1,2,3]
b=[];
arr.forEach(item=>{
    b.push(item)
})
console.log(b);//[1, 2, 3]
//或：
//var b=([...arr])
//var b = arr.slice(0,)

var arr = [{name:"we"},{name:"ni"},{name:"ta"}];
var res = [...arr]//浅拷贝
res[0].name = "huang";
console.log(arr);//[{name: "huang"},{name: "ni"},{name: "ta"}]

//接上
 res.push({name:"zai"})
 console.log(arr);//不变，res有zai，arr没有

Array,Object复杂类型的深拷贝

var arr = [{name:"we"},{name:"ni"},{name:"ta"}];
function deepClone(obj){
    //1.识别是否为数组或对象
    let result;
    if(typeof obj == "number"||obj == null||typeof obj =="boolean"||typeof obj == "string"){
        return obj;
    }
    if(obj instanceof Array || typeof obj == "object"){//instanceof:实例；typeof：类型
        console.log(obj);
        //2.对拷贝的值作初始值设定
        if(obj instanceof Array){
            result = [];
        }else if(typeof obj == "object"){
            result = {}
        }
        console.log(result);
        //3.将obj克隆到result
        for(let key in obj){
            // result[key]=obj[key];
            result[key]=deepClone(obj[key]);//递归
            console.log(result);
        }
        return result;
    }else{
        return obj;
    }
}
var res = deepClone(arr);
res[0].name="gai"
console.log(arr);//arr没变

assign

var obj = {
    name:"we",
    age:12
}
var a = Object.assign({},obj);//assign:分配
a.id = 100;
console.log(a);//Object age: 12 name: "we" id:100
console.log(obj);//Object age: 12 name: "we"