js table 列相加

<table id="myTable">
  <tr>
    <th>产品</th>
    <th>数量</th>
    <th>单价</th>
  </tr>
  <tr>
    <td>产品A</td>
    <td>10</td>
    <td>100</td>
  </tr>
  <tr>
    <td>产品B</td>
    <td>20</td>
    <td>200</td>
  </tr>
  <!-- 更多行... -->
</table>
<button id="sumButton">计算数量总和</button>

document.getElementById('sumButton').addEventListener('click', function() {
  var table = document.getElementById('myTable');
  var rows = table.getElementsByTagName('tr');
  var sum = 0;

  // 从第二行开始遍历，因为第一行是表头
  for (var i = 1; i < rows.length; i++) {
    var cells = rows[i].getElementsByTagName('td');
    // 假设“数量”列是第二列
    var quantity = parseInt(cells[1].innerText, 10);
    sum += quantity;
  }

  alert('数量总和为：' + sum);
});

document.getElementById('sumButton').addEventListener('click', function() {
  var sum = Array.from(document.querySelectorAll('#myTable tr:nth-child(n+2) td:nth-child(2)'))
                .reduce((acc, cell) => acc + parseInt(cell.innerText, 10), 0);
  alert('数量总和为：' + sum);
});