gistfile1.txt

$('.quantity-plus').click(function () {
    var total = parseFloat($('.total').html()).toFixed(2);
    console.log('total ' + total);
    var info = $(this).data('info');
    var id = info.item_id;
    var price = info.price;
    var quantity = $('#quantity-' + id).val();
    quantity = parseInt(quantity) + 1;
    total += price;
    var currentTotal = parseFloat(quantity * price).toFixed(2);
    console.log(currentTotal);
    $('#amount-' + id).html(currentTotal);
    $('.total').html(total);
});