Javascript 如何使用jQuery汇总表中未定义数量的输入？

我有一个表，其中有未定义的行数，这意味着用户可以在客户端添加/删除行。我想做的是，当有人在两个输入（数量和速率）中输入新值时，我想做一些加法和乘法，并将其作为和输出到页面

每行有数量和比率。每行应有一个总计=数量*比率。然后，我想把所有的总数加起来算作总数。我希望能够做到这一点，作为一个用户客户端输入他们的信息。以下是字段的外观：

     <tbody id='line-items'>
        <tr class='fields'>
          <td><input id="invoice_invoice_line_items_attributes_0__destroy" name="invoice[invoice_line_items_attributes][0][_destroy]" type="hidden" value="false" /><a href="javascript:void(0)" class="remove_nested_fields" data-association="invoice_line_items">X</a></td>
          <td><input id="invoice_invoice_line_items_attributes_0_description" label="false" name="invoice[invoice_line_items_attributes][0][description]" size="30" type="text" /></td>
          <td><input class="input-mini" id="invoice_invoice_line_items_attributes_0_quantity" label="false" name="invoice[invoice_line_items_attributes][0][quantity]" size="30" type="text" /></td>
          <td><input class="input-mini" id="invoice_invoice_line_items_attributes_0_rate" label="false" name="invoice[invoice_line_items_attributes][0][rate]" size="30" type="text" /></td>
        </tr>
        <tr class='fields'>
          <td><input id="invoice_invoice_line_items_attributes_1__destroy" name="invoice[invoice_line_items_attributes][1][_destroy]" type="hidden" value="false" /><a href="javascript:void(0)" class="remove_nested_fields" data-association="invoice_line_items">X</a></td>
          <td><input id="invoice_invoice_line_items_attributes_1_description" label="false" name="invoice[invoice_line_items_attributes][1][description]" size="30" type="text" /></td>
          <td><input class="input-mini" id="invoice_invoice_line_items_attributes_1_quantity" label="false" name="invoice[invoice_line_items_attributes][1][quantity]" size="30" type="text" /></td>
          <td><input class="input-mini" id="invoice_invoice_line_items_attributes_1_rate" label="false" name="invoice[invoice_line_items_attributes][1][rate]" size="30" type="text" /></td>
        </tr>
        <tr class='fields'>
          <td><input id="invoice_invoice_line_items_attributes_2__destroy" name="invoice[invoice_line_items_attributes][2][_destroy]" type="hidden" value="false" /><a href="javascript:void(0)" class="remove_nested_fields" data-association="invoice_line_items">X</a></td>
          <td><input id="invoice_invoice_line_items_attributes_2_description" label="false" name="invoice[invoice_line_items_attributes][2][description]" size="30" type="text" /></td>
          <td><input class="input-mini" id="invoice_invoice_line_items_attributes_2_quantity" label="false" name="invoice[invoice_line_items_attributes][2][quantity]" size="30" type="text" /></td>
          <td><input class="input-mini" id="invoice_invoice_line_items_attributes_2_rate" label="false" name="invoice[invoice_line_items_attributes][2][rate]" size="30" type="text" /></td>
        </tr>
      </tbody>

它抓取了所有的行，但我不确定如何跳过ID中的数字，并检查ID的最后一个字，以确保它是数量或速率

var sum = 0;
$('#line_items input[id$="quantity"]').each(function() {
  sum += parseInt($(this).val());
});

---

如果数字是浮点数，也可以使用parseFloat

显示您的尝试，我们不为您编写代码

var sum = 0;
$('#line_items input[id$="quantity"]').each(function() {
  sum += parseInt($(this).val());
});