I make a dynamic form, if i delete a row then in loop result is NaN of the deleted element i want when i delete element its 0 value pass not NaN. Like i delete 5th element when 1=5 it shows NaN. How to remove this error and instead 0 will be add in sum value, how i do?

$(body).on('change', '.quantity', function() {

    var that = $(this);

    if ($('#itemcounter').val()==){

        $('#itemscounter').val(1);

        var counter=$('#itemscounter').val();

        var quantity=$('#quantity').val();

        var unitprice=$('#unitprice').val();

        var linetotal=quantity*unitprice;

        that.parent().find('.linetotal').val(linetotal) 

        $(#invoicetotalamount).val(+linetotal)

        var discount=document.getElementById('discount').value ;

        var discountamount= discount/100 * linetotal;

        var amount=linetotal-discountamount;

        $(#balanceamount).val(+amount);



    } else {            

        var counter=$('#itemscounter').val();

        var quantity=$('#quantity').val();

        var unitprice=$('#unitprice').val();

        var linetotal=quantity*unitprice;

        $('#linetotal').val(+linetotal);

        var sum=linetotal;



        for (i = 2; i <=counter; i++) {

            var quantity=parseFloat($('#quantity' + i).val());

            var unitprice=parseFloat($('#unitprice' + i).val());

            var linetotal=quantity*unitprice;

            $('#linetotal' + i).val(+linetotal);

            alert(sum);         

            sum=+sum +(+(linetotal));           

        }



        $(#invoicetotalamount).val(+sum); 

        var discount=document.getElementById('discount').value ;

        var discountamount= discount/100 * sum;

        var amount=sum-discountamount;

        $(#balanceamount).val(+amount);

    }

});