使用解构获取嵌套数组的长度

const nestedArray = [1, 2, [3, 4, [5, 6, 7], 8], 9];

const getNestedArrayLength = (arr) => {
  let length = 0;
  for (const item of arr) {
    if (Array.isArray(item)) {
      length += getNestedArrayLength(item);
    } else {
      length++;
    }
  }
  return length;
};

const { length } = nestedArray;
const nestedArrayLength = getNestedArrayLength(nestedArray);

console.log(length); // 输出：4
console.log(nestedArrayLength); // 输出：9