Looping through form elements in javascript and adding the fetched values

I'm trying to create a simple form which calculates the values in every input field which has subtotal at the start of the name attribute:

<script type="text/javascript" src="jq.js"></script>

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

var qty = 0;
var price = 0;
var subtotal = 0;
var qty_r = [];
var price_r = [];
var subs_r = [];
var total = 0;

$('input[name^=qty]').each(function(index) {
    qty_r[index] = $(this).val();
});

$('input[name^=price]').each(function(index){
    price_r[index] = $(this).val();
});

var j = 0;
for(j = 0; j<=2; j++){

    subs_r[j] = parseInt(price_r[j]) * parseInt(qty_r[j]);

}




$('input[name^=subtotal]').each(function(index){
    $(this).val(subs_r[index]);
});


$('input[name^=qty]').keyup(function(){
    var basis = $(this).attr("id");
    var numbasis = basis.toString();

    qty = $(this).val();
    price = $('input[name=' + numbasis + ']').val();


    subtotal = parseInt(qty) * parseInt(price);

    $("#subtotal" + numbasis).val(subtotal);

This is the part where I'm having trouble:

$("input[name=subs]").each(function(index){
            total = parseInt($(this).val()) + total;
            $('#total').val(total);

        });

});




});
</script>

And here's where the data which being calculated comes from:

 <?php $products = array(array("prodname"=>"mais", "qty"=>5, "price"=>15), array("prodname"=>"strawberry", "qty"=>7, "price"=>25), array("prodname"=>"kambing", "qty"=>14, "price"=>3)); ?>
    <table border="1">
    <tr>
    <th>Product</th>
    <th>Qty</th>
    <th>Price</th>
    <th>Subtotal</th>
    </tr>
    <?php foreach($products as $key=>$prods){

    ?>
    <tr>
    <td><input type="text" name="prodname<?php echo $key; ?>" value="<?php echo $prods['prodname'];  ?>"/></td>
    <td><input type="text" id="<?php echo $key; ?>" name="qty<?php echo $key; ?>"开发者_如何学编程 value="<?php echo $prods['qty']; ?>"/></td>
    <td><input type="text" name="<?php echo $key; ?>" id="price<?php echo $key; ?>" value="<?php  echo $prods['price']; ?>"/></td>
    <td><input type="text" name="subs" id="subtotal<?php echo $key; ?>" /></td>
    </tr>

    <?php } ?>

    </table>
Total: <input type="text" id="total"/><br/>

The problem is that I'm always getting NaN as a result.

If you're getting NaN you're probably trying to parseInt something that has a return value of NaN. You can do

$("input[name=subs]").each(function(index) {
    total = (parseInt($(this).val(), 10) || 0) + total;
    $('#total').val(total);
});

Wich will always only add numbers to total.

Let's make that a possible answer, try using:

total = parseInt($(this).val()) + parseInt(total);

Also make sure $(this).val() has a proper value everywhere. If it's blank you will get NaN as a result. For almost any other you will get the right result: http://www.w3schools.com/jsref/jsref_parseInt.asp

It looks like you might be using the wrong selector to set the subtotal values you're using to do the final calculation. Shouldn't it be this:

$('input[id^=subtotal]').each(function(index){
    $(this).val(subs_r[index]);
});