text: /**
   * @param {string} s
   * @return {string}
   */
  var longestPalindrome = function (s) {
      let maxLength = 0, left = 0, right = 0
      for (let i = 0; i < s.length; i++) {
          let singleCharLength = getPalLenByCenterChar(s, i, i)
          let doubleCharLength = getPalLenByCenterChar(s, i, i + 1)
          let max = Math.max(singleCharLength, doubleCharLength)
          if (max > maxLength) {
              maxLength = max
              left = i - parseInt((max - 1) / 2)
              right = i + parseInt(max / 2)
          }
      }
      return s.slice(left, right + 1)
  };
  
  function getPalLenByCenterChar(s, left, right) {
      // 中间值为两个字符，确保两个字符相等
      if (s[left] != s[right]){
          return right - left // 不相等返回为1个字符串
      }
      while (left > 0 && right < s.length - 1) {
          // 先加减再判断
          left--
          right++
          if (s[left] != s[right]){
              return right - left - 1
          }
      }
      return right - left + 1
  }
  
  console.log(longestPalindrome("cbbd"))