array扩展

1.Array.from
作用将类数组转为真的数组

var div = document.querySelectorAll('div')
Array.from(div)

2.includes

[1,2,3,4,5].includes(3) //true

3.find findIndx

var arr = [1,23,100,12]
arr.find(it => it > 12)
//23 值
arr.findIndex(it => it > 12)
//1 下标

4.扩展运算符

var a = [12,23,1]
var b = [100,...a]
(4) [100, 12, 23, 1]

5.flat

var arr = [[1,2,3],[1,23,[23,90]]]
arr.flat()
//[1, 2, 3, 1, 23, Array(2)]