168. Excel 表列名称

/**
 * @param {number} columnNumber
 * @return {string}
 */
var convertToTitle = function (columnNumber) {
  const arrMap = ['A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', 'K', 'L', 'M', 'N', 'O', 'P', 'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X', 'Y', 'Z']
  let reNumber = columnNumber
  let result = ''
  while (reNumber > 0) {
    reNumber--
    const index = reNumber % 26
    result = arrMap[index] + result
    reNumber = Math.floor(reNumber / 26)
  }
  return result
}