[jQuery] Having trouble with += and toFixed for some reason

[jQuery] Having trouble with += and toFixed for some reason


Here is my code:
<pre>
    <script type="text/javascript">
        //on page load
        $(document).ready(function() {
            //add up the cart totals and display on the page
            //setup default values
            var bagqty            = '';
            var bagtotal         = '';
            //get all table rows
            $('#shoppingcart tbody tr').each(function() {
                //get the row's price, remove the $
                var price = parseFloat($('.itemprice', this).text().replace(/^[^
\d.]*/, ''));
                //make sure its a number
                price = isNaN(price) ? 0 : price;
                //get the row's quantity
                var qty = parseInt($('.itemqty', this).text());
                //get the item's shipping amount
                var ship = parseFloat($('.itemshipping', this).text().replace(/^[^
\d.]*/, ''));
                //make sure its a number
                ship = isNaN(ship) ? 0 : ship;
                //calculate the extended price
                var extprice = (qty * price) + ship;
                //add back in the $ sign and write to the page
                $('.itemextprice', this).text('$' + extprice.toFixed(2));
                //add to totals
                bagqty += qty;
                bagtotal += extprice;
            });
            //return the totals
            $('.bagtotal').text('$' + bagtotal.toFixed(2));
        });
    </script>
</pre>
I have 2 issues-
1- the bagqty += qty; and bagtotal += extprice; calculations return
appended values, not added. So if there are 2 products and the bagqty
values are 5 and 3 I get 53 instead of 8.
2- the $('.bagtotal').text('$' + bagtotal);    line won't work. I get a
bagtotal.toFixed is not a function error. It works fine in the
itemextprize calculation up higher.
Any ideas?