jQuery自动计算

My goal is to be able to compute the subtotal from given 2 values. First value is given, and the other one is inputted. The subtotal changes when the user inputs a different value into the quantity field.

Here's the jquery code that I'm using:

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

$('input[id^=qty]').keyup(function(){

    var parentDiv = $(this).closest('#axd');

    var curprice=parentDiv.find('input[id^=price]').val();
    var curqty= this.value;
    var curtotal=curprice * curqty;

    parentDiv.find('input[id^=comp]').val(curtotal);
});




});

And here's the body:

 <tr>
    <form name="cartform" method="get" onsubmit="return validate_form(this);" action="checkout.php">
        <div id="axd">
            <td><?php echo $name; ?></td>

            <input type="hidden" id="pids" name="ids[]" value="<?php echo $id; ?>"/>
            <input type="hidden" name="qoh[]" value="<?php echo $qtyhand; ?>"/>

            <input type="hidden" name="dprice[]" value="<?php echo $dsprice; ?>"/>


            <td><?php echo $qtyhand; ?></td>


            <td><input type="text" id="<?php echo 'qty' . $id; ?>" name="qbuys[]" value=""/></td>


            <input type="hidden" id="<?php echo 'price' . $id; ?>" name="sprice[]" value="<?php echo $ssprice; ?>"/>
            <td><?php echo $ssprice; ?></td>

            <td><input type="text" name="subtot[]" id="<?php echo 'comp' . $id; ?>" value=""/></td> 

            <td><a href="viewcart.php?action=zeroline&id=<?php echo $id; ?>"><img src="../img/system/delete-icon.png"></img></a></td>

        </div>
    </form>
    </tr>

The error is that it doesn't output any value at all. What's wrong with my code? Here's the link to the full version of the code: http://cu.pastebin.com/sWxFV6Hg

why not just assign each field an ID and use the classic javascript instead of jquery for one multiply and a sum.

go like this: - assign ids then write this function:

function operation()
{
  var op1 = document.getElementById('id1').value;
  var op2 = document.getElementById('id2').value;
  document.getElementById('wherever_you_want_it').value = op1 (whatever operation) op2;
}

Call the function on whatever event you want. And... done it.