在下拉列表中添加表行，选择并删除行。只添加一次来自特定下拉列表select的行

<table id="myTable">
  <thead>
    <tr>
      <th>列1</th>
      <th>列2</th>
      <th>操作</th>
    </tr>
  </thead>
  <tbody>
    <tr>
      <td>
        <select id="mySelect">
          <option value="1">选项1</option>
          <option value="2">选项2</option>
          <option value="3">选项3</option>
        </select>
      </td>
      <td>内容1</td>
      <td>
        <button onclick="addRow()">添加行</button>
      </td>
    </tr>
  </tbody>
</table>

function addRow() {
  var table = document.getElementById("myTable");
  var select = document.getElementById("mySelect");
  var selectedOption = select.options[select.selectedIndex];
  
  var newRow = table.insertRow(table.rows.length);
  var cell1 = newRow.insertCell(0);
  var cell2 = newRow.insertCell(1);
  var cell3 = newRow.insertCell(2);
  
  cell1.innerHTML = selectedOption.text;
  cell2.innerHTML = "内容2";
  cell3.innerHTML = "<button onclick='deleteRow(this)'>删除行</button>";
}

function deleteRow(button) {
  var row = button.parentNode.parentNode;
  row.parentNode.removeChild(row);
}