扩展运算符

spread扩展运算符

1.概念

扩展运算符（spread）也是三个点（...）。它好比 rest 参数的逆运算，将一个数组转为用逗号分隔的参数序列，对数组进行解包。

2.应用

（1）数组的合并

const arr1 = [1, 2, 3]
const arr2 = ['a', 'b', 'c']
const arr3 = [...arr1, ...arr2]
console.log(arr3)   //[1,2,3,'a','b','c']

（2）数组的克隆(深拷贝)

const arr4=['one','two','three']
const arr5=[...arr4]
arr5[1]='qq'
console.log(arr5) //['one','qq','three']
console.log(arr4) //['one','two','three']