/**
 * @param {number[]} digits
 * @return {number[]}
 */
var plusOne = function(digits) {
  let i = digits.length;
  let carry = 1;
  let tmp;
  const res = [];
  while(i > 0 || carry) {
    tmp = (--i >= 0 ? digits[i] : 0) + carry;
    carry = tmp / 10 | 0;
    res.unshift(tmp % 10);
  }
  return res;
};