ES6中扩展运算符的作用

1.将一个数组变为一个以空格分隔的参数序列

var arr=[1,2,3,4,5,6];

console.log(...arr);// 1 2 3 4 5 6

2.复制(浅拷贝)

数组的复制

var arr1=[1,2,3,4,[5]];

var arr2=[...arr1];

arr1[0]=10;

arr1 [4] [0]=100;

console.log(arr1);

console.log(arr2);

对象的复制

var obj1={name:"张三"，age：18，person:{name:"李四"}}；

var obj2={...obj1};

obj1.age=20;//深拷贝

obj1.person.name="王五" //浅拷贝

console.log(obj1);

console.log(obj2);

合并

数组的合并

var arr3=[1,2,3,4]

var arr4=[5,6,7]

var arr5=[...arr3,...arr4];

console.log(arr5);//[1,2,3,4,5,6,7]

对象的合并

var obj3={name="张三"}

var obj4={age:18}

var obj5={...obj3,...obj4}

console.log(obj5);

字符串改为数组

var myArr=[...'hello'];

console.log(myArr);//["h","e","l","l","o"]