如何从表行的bootstrap 4下拉列表中获取id值？

<table>
  <tr>
    <td>
      <select id="myDropdown" class="form-control">
        <option value="1">Option 1</option>
        <option value="2">Option 2</option>
        <option value="3">Option 3</option>
      </select>
    </td>
  </tr>
</table>

var selectedOptionId = $("#myDropdown option:selected").val();
console.log(selectedOptionId);

var dropdown = document.getElementById("myDropdown");
var selectedOptionId = dropdown.options[dropdown.selectedIndex].value;
console.log(selectedOptionId);