[Vlasenko Fedor]

<table border="1" id="testTable">
  <tr>
    <td width="20" height="20"></td>
    <td width="20" height="20"></td>
  </tr>
  <tr>
    <td width="20" height="20"></td>
    <td width="20" height="20"></td>
  </tr>
</table>
<script>
testTable.addEventListener("click", ({target}) => {
  target.tagName === "TD" && alert(`Координаты X: ${target.cellIndex}\nКоординаты Y: ${target.parentNode.rowIndex}`);
})
</script>

Вариант