JOLT transformation filter a list about the first string element

Solution 1:

You have some values that ended with numbers. So we can match all values that ended with the number, and we have a real string in the last.

[
  {
    "operation": "shift",
    "spec": {
      "firstString": {
        "*": {
          "*0": "",
          "*1": "",
          "*2": "",
          "*3": "",
          "*4": "",
          "*5": "",
          "*6": "",
          "*7": "",
          "*8": "",
          "*9": "",
          "*": {
            "$": "readingS"
          }
        }
      }
    }
  }, {
    "operation": "shift",
    "spec": {
      "*": {
        "*": "&"
      }
    }
  }
]