javascript - Jquery : Product between 2 lists of inputs into a 3rd list -

i don't have experience in jquery, i'm facing following challenge

i have following table

<table>     <thead>         <tr>             <td>qty</td>             <td>description</td>             <td>unit price</td>             <td>total price</td>         <tr>     </thead>     <tbody>         <tr id="itemrow">             <td><input type="text" name="quantity"/></td>             <td><input type="text" name="description"/></td>             <td><input type="text" name="unitprice"/>/td>             <td><input type="text" name="totalprice"/></td>         <tr>     </tbody> </table>  <input type="text" name="total"/> 

additionally, i'm able clone #itemrow many times required, enlarging amount of items.

the idea calculate total price each row (by quantity * unitprice) , assign totalprice. , assign sum of totalprice total.

this javascript i'm using, error says "cantidades[i].val() not function"

function calculate(){      var $total = $('#total');      var $cantidades = $('input[name=quantity]')     var $unitarios  = $('input[name=unitprice]')     var $totales = $('input[name=totalprice]')      var len = $cantidades.length;      $total.val(0);      (var = 0; < len; i++){         // calculate total row. error here!         $totales[i].val($cantidades[i].val() * $unitarios[i].val());          // accumulate total           $total.val($totalexento.val() + $totales[i].val());     } } 

what missing? think i'm not getting "jquery objects" selector i'm not sure hot this.

thanks in advance!

this line: var $cantidades = $('input[name=quantity]') retrieves jquery instance cannot accessed did $cantidades[i].

fix this:

var singleelementcantidades = $($cantidades[i]); singleelementcantidades.val(); 

what happened $('input[name=quantity]') retrieves array instance of jquery. , when access content using cantidades[i] not managing jquery instance anymore, accessing else wich doesn't have definition of val.