几种方法如下

1. toString + split
2. join + split
3. Array.prototype.flat(Infinity)
4. reduce + concat + isArray 递归实现
5. Use a stack 堆栈非递归
6. Use Generator function 生成器

toString + split

function flatDeep(array: any[]): number[] {
  return array
    .toString()
    .split(',')
    .map((item) => Number(item))
}

join + split

function flatDeep(array: any[]): number[] {
  return array
    .join()
    .split(',')
    .map((item) => Number(item))
}

Array.prototype.flat(Infinity)

function flatDeep(array): number[] {
  return array.flat(Infinity)
}

reduce + concat + isArray 递归实现

function flatDeep(array: any[], depth = 1): number[] {
  return depth > 0
    ? array.reduce((pre, cur, index, arr) => {
        return pre.concat(Array.isArray(cur) ? flatDeep(cur, depth - 1) : cur)
      }, [])
    : array.slice()
}

Use a stack 堆栈非递归

// non recursive flatten deep using a stack
// note that depth control is hard/inefficient as we will need to tag EACH value with its own depth
// also possible w/o reversing on shift/unshift, but array OPs on the end tends to be faster
function flatten(input) {
  const stack = [...input]
  const res = []
  while (stack.length) {
    // pop value from stack
    const next = stack.pop()
    if (Array.isArray(next)) {
      // push back array items, won't modify the original input
      stack.push(...next)
    } else {
      res.push(next)
    }
  }
  // reverse to restore input order
  return res.reverse()
}

const arr = [1, 2, [3, 4, [5, 6]]]
flatten(arr)
// [1, 2, 3, 4, 5, 6]

MDN (opens new window)

Use Generator function 生成器

function* flatten(array, depth) {
  if (depth === undefined) {
    depth = 1
  }
  for (const item of array) {
    if (Array.isArray(item) && depth > 0) {
      yield* flatten(item, depth - 1)
    } else {
      yield item
    }
  }
}

const arr = [1, 2, [3, 4, [5, 6]]]
const flattened = [...flatten(arr, Infinity)]
// [1, 2, 3, 4, 5, 6]

MDN (opens new window)

总结

数组扁平化的方法有：

1. toString + split
2. join + split
3. Array.prototype.flat(Infinity)
4. reduce + concat + isArray 递归实现
5. Use a stack
6. Use Generator function 生成器