Select 출력 입니다.

</p>

<p><select id="txt">

  <option value="">선택 </option>

  <option value="A"> A </option>

  <option value="B"> B </option>

  <option value="C"> C </option>

</select>

<div id="result"></div></p>

<p><script>

  const result = document.querySelector("#result");

  const txt = document.querySelector("#txt");

  const num = [1, 4, 5];

  let str = [];

  const A = ["", "AA", "AB", "AC", "AD", "AE", "AF", "AG"];

  const B = ["", "BA", "BB", "BC", "BD", "BE", "BF", "BG"];

  const C = ["", "CA", "CB", "CC", "CD", "CE", "CF", "CG"];</p>

<p>  txt.addEventListener('change', () => {

    const selectedValue = txt.value;

    str = num.map((index) => {

      switch (selectedValue) {

        case "A":

          return A[index];

        case "B":

          return B[index];

        case "C":

          return C[index];

        default:

          return "";

      }

    });

    result.innerHTML = str.join(", ");

  });

</script>