Multiline String, Get Range Lines

// GraalJS Script (engine type: 2)

//////// START "main()" /////////////////////////////////////////////////////////////////
main();
function main(){ 

//// == Config Retrieving / 工程コンフィグの参照 ==
const strInput         = configs.get( "StrConfA1" );          /// REQUIRED //////////////
  if( strInput       === "" ){
    throw new Error( "\n AutomatedTask ConfigError:" +
                     " Config {A1: Text} is empty \n" );
  }
const strBeginIndex    = configs.get( "StrConfB1" );          /// REQUIRED //////////////
  if( strBeginIndex  === "" ){
    throw new Error( "\n AutomatedTask ConfigError:" +
                     " Config {B1: BeginIndex} is empty \n" );
  }
  const numBeginIndex  = parseInt( strBeginIndex, 10 );
  if( isNaN( numBeginIndex ) ){
    throw new Error( "\n AutomatedTask ConfigError:" +
                     " Config {B1: BeginIndex} must be an integer \n" );
  }
const strEndIndex      = configs.get( "StrConfB2" );          // NotRequired ////////////
  const numEndIndex    = parseInt( strEndIndex, 10 );
  if( strEndIndex    !== "" ){
    if( isNaN( numBeginIndex ) ){
      throw new Error( "\n AutomatedTask ConfigError:" +
                       " Config {B2: EndIndex} must be an integer or empty \n" );
    }
  }
const strPocketOutput  = configs.getObject( "SelectConfC1" ); /// REQUIRED //////////////


//// == Data Retrieving / ワークフローデータの参照 ==
// (Nothing. Retrieved via Expression Language in Config Retrieving)


//// == Calculating / 演算 ==
const arrInput = strInput.split("\n");
let arrOutput;

/// OutputLog and Extract
if( strEndIndex    === "" ){
  engine.log( " AutomatedTask RuntimeLog:" +
              " Range: from " + numBeginIndex + " to (end)" );
  arrOutput  = arrInput.slice( numBeginIndex );
}else{
  engine.log( " AutomatedTask RuntimeLog:" +
              " Range: from " + numBeginIndex + " to " + numEndIndex );
  arrOutput  = arrInput.slice( numBeginIndex, numEndIndex );
}

let strOutput = arrOutput.join("\n");

//// == Data Updating / ワークフローデータへの代入 ==
engine.setData( strPocketOutput, strOutput );


} //////// END "main()" /////////////////////////////////////////////////////////////////

/*
Notes:
- When the process reaches this automated task, the Text in the string data is automatically processed.
    - TSV data, Access log, Email body, etc.
    - {Number of lines} = {Number of line breaks} + 1
- The range specified by the start line (Begin Index) and end line (End Index) is extracted.
    - Index starts at zero. The Index on the first line is "0". (10-line text: 0,1,2,3,4,5,6,7,8,9)
        - If a negative value for Index, interpreted as the value subtracted from the number of lines.
        - If "-1" is specified in 10 lines of text, it is the same as if "9" is specified.
    - End Index is optional. If omitted, the entire part will be extracted.
        - Even if End Index is specified to exceed the Index of the last row, the end will be extracted.
    - A case where an empty string is returned.
        - {Begin Index} >= {End Index}
        - {Begin Index} > (Index of the last line)
    - Example of range specification
        - Extract the first 5 lines (0,1,2,3,4,5,,, to 0,1,2,3,4):
            - {Begin Index}: `0`
            - {End Index}: `5`
        - Extract only the 3rd line (0,1,2,3,4,5,,, to 2):
            - {Begin Index}: `2`
            - {End Index}: `3`
        - Delete one first line (header row) (0,1,2,3,,,N to 1,2,3,,,N):
            - {Begin Index}: `1`
            - {End Index}: (empty)
        - Delete one last line (footer row) (0,1,2,,,N-1,N to 0,1,2,,,N-1):
            - {Begin Index}: `0`
            - {End Index}: `-1`

APPENDIX:
- The range specification is the same as the JavaScript `slice ()` method.
    - https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/slice
    - https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String/slice
- 10-line text：0,1,2,3,4,5,6,7,8,9
    - {Begin Index}: `-10`
        - Output Line: 0,1,2,3,4,5,6,7,8,9
    - {Begin Index}: `5`, {End Index}: `20`
        - Output Line: 5,6,7,8,9
- When setting an index by referring to numeric, set an EL expression using arithmetic operations.
    - Extract only (N+1) line; (Index N)
            - {Begin Index}: `#{#q_numN}`
            - {End Index}: `#{#q_numN + 1}`


Notes-ja:
- 案件が自動処理工程に到達した際、文字列型データに保存されているTextが自動的に加工されます。
    - TSVデータ、アクセスログ、メール本文など
    - {行の数} = {改行の数} + 1
- 開始行（Begin Index）と終了行（End Index）で指定された範囲が抽出されます。
    - Index はゼロ始まりです。1行目の Index は "0" です。（10行テキストの場合：0,1,2,3,4,5,6,7,8,9）
        - Index に負の値が指定された場合、テキストの全行数から減算された値と解釈されます。
        - 10行のテキストで "-1" が指定された場合は "9" が指定された場合と同じ処理になります。
    - End Index は省略可能です。省略した場合は末尾までが抽出されます。
        - End Index に最終行の Index を超える値が指定された場合も、末尾までが抽出されます。
    - 空文字列が返されるケース。
        - {Begin Index} >= {End Index}
        - {Begin Index} > (最終行のIndex)
    - 範囲指定の例
        - 先頭の5行を抽出 (0,1,2,3,4,5… ⇒ 0,1,2,3,4):
            - {Begin Index}: `0`
            - {End Index}: `5`
        - 3行目だけを抽出 (0,1,2,3,4,5… ⇒ 2):
            - {Begin Index}: `2`
            - {End Index}: `3`
        - 先頭行（ヘッダ行）を1行削除 (0,1,2,3,…,N ⇒ 1,2,3,…,N):
            - {Begin Index}: `1`
            - {End Index}: `(empty)`
        - 最終行（フッタ行）を1行削除 (0,1,2,…,N-1,N ⇒ 0,1,2,…,N-1):
            - {Begin Index}: `0`
            - {End Index}: `-1`

APPENDIX-ja:
- 範囲の指定方法は、JavaScript `slice()` メソッドと同様です。
    - https://developer.mozilla.org/ja/docs/Web/JavaScript/Reference/Global_Objects/Array/slice
    - https://developer.mozilla.org/ja/docs/Web/JavaScript/Reference/Global_Objects/String/slice
- 10行テキストの場合：0,1,2,3,4,5,6,7,8,9
    - {Begin Index}: `-10`
        - Output Line: 0,1,2,3,4,5,6,7,8,9
    - {Begin Index}: `5`, {End Index}: `20`
        - Output Line: 5,6,7,8,9
- 数値型データを参照してインデックスを設定する場合、四則演算を使ったEL式設定が便利です。
    - N+1行目 (Index N) だけを抽出
            - {Begin Index}: `#{#q_numN}`
            - {End Index}: `#{#q_numN + 1}`
*/