js实现购物车数量的自增与自减

<script type="text/JavaScript"> function qtyUpdate(kind){     var f = document.form1;     var c = f.qty.value;     if(kind == "up"){         c++;     }else if(kind == "down"){         if(c > 1) c--;     }     f.qty.value = c; } </script>

<FORM  name=form1 > <TABLE border=0 cellSpacing=0 cellPadding=0> <TBODY> <TR> <TD rowSpan=2><INPUT value=2 readOnly size=5 name=qty></TD> <TD rowSpan=2 width=3></TD> <TD><A href="javascript:qtyUpdate('up')"><IMG src="btn_up.gif" width=11 height=8></A></TD> </TR> <TR> <TD align=right><A href="javascript:qtyUpdate('down')"><IMG src="btn_down.gif" width=11 height=8></A></TD> </TR> </TBODY> </TABLE> </FORM>

或

<script type="text/javascript" src="/wang_7380031@126/blog/js/jquery-1.4.2.min.js"></script>

<script type="text/JavaScript">

function qtyUpdate(kind,id){

    var num = parseInt($('#amount_'+id).val());

    if(kind == "up"){          

            $('#amount_'+id).val(num+1);

    }else{

        if(num>1){

                $('#amount_'+id).val(num-1);

        }

    }

}

</script>

                                    <A href="javascript:qtyUpdate('down','<?php echo $key; ?>')" ><IMG src="/wang_7380031@126/blog/p_w_picpaths/down1.jpg"></A>

                                    <input id='amount_<?php echo $key;?>' value="1" type="text" name='qty[]' size="3">&nbsp;

                                    <A href="javascript:qtyUpdate('up','<?php echo $key; ?>')" ><IMG src="/wang_7380031@126/blog/p_w_picpaths/up1.jpg"></A>