扩展运算符

将数组转为用逗号分隔的参数序列

 var arr=["唱","跳","rap"]
 console.log(arr)//(3)['唱', '跳', 'rap']这里输出的是数组
 console.log(...arr);//唱 跳 rap 
 //这里看起来没","  实际结果为 "唱","跳","rap"
 //因为console.log()会把多个参数值的逗号用作分隔符而不显示出来，所以控制台上面没有打印逗号
 //console.log(...arr);相当于console.log("唱","跳","rap");
 console.log("唱","跳","rap");// 唱 跳 rap 

合并数组

            var arr1=[1,2,3];
            var arr2=[4,5,6];
            var arr3=[...arr1,...arr2];
            console.log(arr3);    

字符串改数组

 let Arr=[...'str']
 console.log(Arr);

浅拷贝

        let a1=[1,2,3,[4]]
        let a2=[...a1]
        a1[0]="change"
        a1[3][0]="s"
        console.log(a1);
        console.log(a2);
        //obj
        let obj={name:"zs",age:"18",person:{name:"ls"}};
        let obj1={...obj};
        obj.name="cs"
        obj.person.name="ww"
        console.log(obj);
        console.log(obj1);