缩减多维数组，得到给定数组的sum/avg/min/max

function reduceMultiDimensionalArray(arr) {
  let sum = 0;
  let count = 0;
  let min = Infinity;
  let max = -Infinity;

  function traverseArray(arr) {
    for (let i = 0; i < arr.length; i++) {
      if (Array.isArray(arr[i])) {
        traverseArray(arr[i]);
      } else {
        sum += arr[i];
        count++;
        min = Math.min(min, arr[i]);
        max = Math.max(max, arr[i]);
      }
    }
  }

  traverseArray(arr);

  const average = sum / count;

  return {
    sum,
    average,
    min,
    max,
  };
}

const arr = [[1, 2, 3], [4, 5, 6], [7, 8, 9]];
const result = reduceMultiDimensionalArray(arr);
console.log(result);