Function flatFnn

src/js/arrayFunction/array-reduce.js:19–21

(arr)

// 多维数组展开
const flatFnn = (arr) => arr.reduce(
  (prev, curr) => (Array.isArray(curr) ? prev.concat(flatFnn(curr)) : prev.concat(curr)), [],
)

let oldArr = [1, [2, [3, [4, [5]]]]]
let newArr = flatFnn(oldArr)