编辑代码

formatTimeReverse = (timeString) => {
  if (typeof timeString === "undefined") return "";
  let index = 0;
  if (timeString.length === 8) {
    return (
      timeString.slice(index, (index += 2)) +
      timeString.slice((index += 1), (index += 2)) +
      timeString.slice((index += 1), (index += 2))
    );
  }
  if (timeString.length === 10) {
    return (
      timeString.slice(index, (index += 4)) +
      timeString.slice((index += 1), (index += 2)) +
      timeString.slice((index += 1), (index += 2))
    );
  }
  if (timeString.length === 19) {
    return (
      timeString.slice(index, (index += 4)) +
      timeString.slice((index += 1), (index += 2)) +
      timeString.slice((index += 1), (index += 2)) +
      timeString.slice((index += 1), (index += 2)) +
      timeString.slice((index += 1), (index += 2)) +
      timeString.slice((index += 1), (index += 2))
    );
  }
};

console.log(formatTimeReverse("2021-04-04 13:34:33"))
console.log(formatTimeReverse("2021-04-04"))
console.log(formatTimeReverse("13:34:33"))