Рассчитайте общую сумму с помощью javascript

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  <script type="text/javascript">
        function FetchData(button) {

            var row = button.parentNode.parentNode;
            var label = GetChildControl(row, "quantity_1").value;
            var label1 = GetChildControl(row, "product_rate_1").value;
            var Multi = parseFloat(label) * parseFloat(label1);
            //var grandtotal = $(this).find('.grand').val();
            GetChildControl(row, "total_price_1").value = Multi;
           
            var tot = 0;
            for (var i = 0; i < Multi.length; i++) {
                if (parseInt(Multi[i].value))
                    tot += parseInt(Multi[i].value);
            }
            document.getElementById('grandTotal').value = tot;
            console.log(+tot)
        };

        function GetChildControl(element, id) {
            var child_elements = element.getElementsByTagName("*");
            for (var i = 0; i < child_elements.length; i++) {
                if (child_elements[i].id.indexOf(id) != -1) {
                    return child_elements[i];
                    console.log(+i)

                }
            }
        };
  </script>
<pre>       <table class="table" id="maintable">
                                <thead>
                                    <tr>
                                            <th class="text-center" width="20%">Item Information*</th> 
                                            <th class="text-center">Batch ID *</th>
                                             <th class="text-center">Expiry  date *</th>
                                            <th class="text-center">Stock/Qnt</th>
                                            <th class="text-center">Quantity *</th>
                                            <th class="text-center">Manufacturer  Price*</th>
                                            <th class="text-center">Total</th>
                                            <th class="text-center">Action</th>
                                        </tr>
                                </thead>
                                <tbody>
                                    <tr class="data-contact-person">
                                        <td>

                                          <input type="text" name="f-name" class="form-control f-name01" /></td>
                                                    
                                         <td>
                                          <input type="text" name="l-name" class="form-control l-name01" /></td>
                                                                                   
                                            <td>
                                              <input type="text" name="email"  class="form-control datepicker" /></td>
                                                                                 
                                       <td >

                                        <input type="text" name="stock" class="form-control stock01" /></td>
                                             
                                            <td>
                                               <input type="text" name="product_quantity" id="quantity_1"  onkeyup="FetchData(this),findTotal()"  placeholder="0.00" value="" min="0" class="form-control qty01" required="required"/></td>
                                                                                  
                                            <td >

                                             <input type="text" name="product_rate" onkeyup="FetchData(this),findTotal()"  id="product_rate_1" placeholder="0.00" value="" min="0"  class="form-control rate01" required="required"/></td>
                                             
                                            <td>
                                             <input type="text" name="total_price" id="total_price_1" value="0.00"  readonly="readonly" class="form-control total_price" /></td>
                                             
                                            <td>

                                               <button type="button" id="btnAdd"  onclick="FetchData(this),findTotal()" class="btn btn-xs btn-primary  classAdd">Add More</button>
                                              
                                            </td>
                                    </tr>
                                </tbody>
                                <tfoot>
                                    <tr>
                                        <td colspan="2">

                                       
                                           <%-- <input type="button" id="add_invoice_item" class="btn btn-info" name="add-invoice-item" onclick="addPurchaseOrderField1('addPurchaseItem');" value="Add New Item" tabindex="11">--%>

                                            <input type="hidden" name="baseUrl" class="baseUrl" value="">
                                        </td>
                                        <td style="text-align:right;" colspan="4">Grand Total:</td>
                                        <td class="text-right">
                                            <input type="text" id="grandTotal" class="text-right form-control" name="grand_total_price" value="0.00" readonly="readonly">
                                        </td>
                                    </tr>
                                </tfoot>
                            </table>
                        </div>

Что я уже пробовал:

<script type="text/javascript">
       function findTotal() {
           var arr = document.getElementsByName('total_price');
           var tot = 0;
           for (var i = 0; i < arr.length; i++) {
               if (parseInt(arr[i].value))
                   tot += parseInt(arr[i].value);
           }
           document.getElementById('grandTotal').value = tot;
           console.log(+tot)
       }

   </script>

Первый ряд становится просчитать всего ,если я динамически добавлять строки
не рассчитываю..

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