How To Simultaneously Add Multiple Products To A Magento Shopping Cart

<script type="text/javascript">
    function processNext(urls, i) {
        var next = i + 1;
        $('processing-text').update('Processing item ' + next);
        if (next < urls.size()) {
            new Ajax.Request(urls[i], {
              method: 'get',
              onComplete: function(transport) {
                processNext(urls, next);
              }
            });
        } else {
            new Ajax.Request(urls[i], {
              method: 'get',
              onComplete: function(transport) {
                window.location.reload();
              }
            });
        }
    }

    function addItemsToCart() {
        $('add-items-to-cart').hide();
        $('waiting').show();

        var addToCartUrls = [];
        $$('input.add').each(function(e){
            if(e.checked == true) {
                var id = e.readAttribute('id').split('_')[1];
                var qty = Number($('qty_' + id).value);
                if (qty < 1) qty = 1;
                addToCartUrls.push($('url_' + id).value + 'qty/' + qty);
            }
        });

        if (addToCartUrls.size() > 0) {
            processNext(addToCartUrls, 0);
        } else {
            $('add-items-to-cart').show();
            $('waiting').hide();
            alert('Please check off the items you want to add.');
        }
    }
</script>

Referred from:
Linden LAN » Blog Archive » How To Simultaneously Add Multiple Products To A Magento Shopping Cart