แก้ code .ให้ด้วยค่ะ คือ อยากให้ total_phone เปลี่ยนมาแสดงผลค่าของ $value_room

<script type="text/javascript">
       function addCommas(nStr) {
        nStr += '';
        x = nStr.split('.');
        x1 = x[0];
        x2 = x.length > 1 ? '.' + x[1] : '';
        var rgx = /(\d+)(\d{3})/;
        while (rgx.test(x1)) {
            x1 = x1.replace(rgx, '$1' + ',' + '$2');
        }
        return x1 + x2;
    }

    //*define object "Bill"
    function Bill(){
        //get form value
        var unit = {
            'water' : document.form2.wvalue.value,
            'fire' : document.form2.fvalue.value,
            'phone' : document.form2.pvalue.value
        }
        var rate = {
            'water' : document.form2.u_water.value,
            'fire' : document.form2.u_fire.value,
            'phone' : document.form2.u_phone.value
        }

        //private function
        this.calc = function(unit, rate){
            unit = parseFloat(unit);
            rate = parseFloat(rate);

            if(!unit || !rate){return 0;}
            return unit * rate;
        }

        //public properties
        this.water = this.calc(unit['water'],rate['water']);
        this.fire = this.calc(unit['fire'],rate['fire']);
        this.phone = this.calc(unit['phone'],rate['phone']);
    }

    function calcBill(){
        var bill = new Bill();

        document.form2.total_water.value = addCommas(bill.water.toFixed(2));
        document.form2.total_fire.value = addCommas(bill.fire.toFixed(2));
        document.form2.total_phone.value = addCommas(bill.phone.toFixed(2));
        document.form2.be_total.value = addCommas((bill.water + bill.fire + bill.phone).toFixed(2));
    }

</script>