Jolt configuration for Middle Initial

Question

Trying to find the middle initial Jolt configuration. Ask is, i need to consider only first character in Middle name return from Json. Also first character should be Alphabet (either caps or small case), else i need to return null.

M. -> M.  
M$ -> M  
$M -> null  
.M -> null  
Mary -> M  
1Mary --> null

Input 1:

{
  "applicant": {
    "firstName": "Mary",
    "middleName": "M.",
    "lastName": "Coker"
  }
}

Input 2:

{
  "applicant": {
    "firstName": "Mary",
    "middleName": "$M",
    "lastName": "Coker"
  }
}

Desired Output for 1:

{
  "applicant": {
    "firstName": "Mary",
    "middleName": "M",
    "lastName": "Coker"
  }
}

Desired Output for 2:

{
  "applicant": {
    "firstName": "Mary",
    "middleName": null,
    "lastName": "Coker"
  }
}

Answer 1

You can use toLower and toUpper functions those have respectively different impacts for letters which are the first characters of middleName s while have no impact on non-alphabetic chars such as

[
  {
    "operation": "modify-overwrite-beta",
    "spec": {
      "*": {
        "middleName": "=substring(@(1,&),0,1)",
        "up": "=toUpper(@(1,middleName))",
        "lw": "=toLower(@(1,middleName))"
      }
    }
  },
  {
    "operation": "shift",
    "spec": {
      "*": {
        "*": "&1.&",
        "up|lw": { "$": "&2.extra.@0" }
      }
    }
  },
  {
    "operation": "modify-overwrite-beta",
    "spec": {
      "*": {
        "extra": "=size"
      }
    }
  },
  {
    "operation": "shift",
    "spec": {
      "*": {
        "*": "&1.&",
        "middleName": { //get rid of the previosly derived "middleName" value
          "": ""
        },
        "extra": {
          "1": { // match middleName with a null 
            //if both of the derived "middleName" values are equal
            "@": "&3.middleName"
          },
          "2": { //keep the derived "middleName" value if the first character is a letter
            //eg.there are two different letters : upper one vs. lower one
            "@2,middleName": "&3.middleName"
          }
        }
      }
    }
  }
]