将相邻元素组合成新的最小2个数组

function combineNeighbouringElements(arr) {
  if (arr.length < 2) {
    return arr;
  }
  const res = [];
  let temp = [arr[0]];
  for (let i = 1; i < arr.length; i++) {
    if (temp.length === 1) {
      temp.push(arr[i]);
    } else if (temp.length === 2) {
      res.push(temp);
      temp = [arr[i]];
    }
  }
  if (temp.length === 2) {
    res.push(temp);
  }
  return res;
}

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