JavaScript arithmetic returns unexpected value

Question

Here is a simple JS snippet,

$("#product_code").live('change',function(){
    $.ajax({
        type:'POST',
        url:baseurl+'ajax/getproduct/'+$(this).val(),
        success:function(productdetails){
            var bill_type = $("#bill_type").val();
            var mrp_value = productdetails['mrp_value'];
            var quantity = productdetails['quantity'];

            $("#product_name").val(productdetails['product_name']);
            $("#packing").val(productdetails['packing']);
            $("#mrp_value").val(productdetails['mrp_value']);
            $("#batch_number").val(productdetails['batch_number']);
            $("#manufacturing_date").val(productdetails['manufacturing_date']);
            $("#expiry_date").val(productdetails['expiry_date']);
            $("#quantity").val(productdetails['quantity']);

            switch(bill_type)
            {
                case 'stockies':
                        var pts_value = 5; //In percent
                        var vat = 5; //In percent
                        var total_value = (mrp_value+(mrp_value*vat/100)-(mrp_value*pts_value/100))*quantity;                               
                    break;
                case 'pharmacy':
                        var pts_value = 3; //In percent
                        var vat = 5; //In percent
                        var total_value = (mrp_value+(mrp_value*vat/100)-(mrp_value*pts_value/100))*quantity;                               
                    break;
                case 'replacement':
                        var pts_value = 0; //In percent
                        var vat = 0; //In percent
                        var total_value = 0;
                    break;
            }

            $("#pts_value").val(pts_value);
            $("#vat").val(vat);

            $("#total_value").val(total_value);
        }
    }); 
});

And the value i'm getting through JSON AJAX request is,

{"stock_id":"1","product_code":"AG123456","product_name":"Test Product","packing_area":"10x10","bottle_size":"170ml","product_type":"bottle","chemical_contents":"HCL","batch_number":"12","manufacturing_date":"2012-03-12","expiry_date":"2014-03-12","quantity":"4","packing":"Hard","purchase_value":"34","sales_value":"36","mrp_value":"35","status":"0","created_date":"2014-04-27 14:05:17","modified_date":null,"deleted_date":null}

If i print the values separately, it is showing,

var mrp_value = 35;
var quantity = 4;

and the assigned values are, var pts_value = 5; var vat = 5;

var total_value = (mrp_value+(mrp_value*vat/100)-(mrp_value*pts_value/100))*quantity;

So, i'm expecting this will execute as follows,

(35 + (35*5/100) - (35*5/100) ) * 4
(35 + (1.75) - (1.75)) * 4
(35 + (0)) * 4
140

But it is returning 1400 as value. Why and where i'm doing the mistake?

I didn't go through your code, but my money's on one or more values being treated as a string instead of as a number. — j08691
– j08691, Commented Apr 30, 2014 at 20:56
All the numbers in the JSON are strings. You could try fixing the server script to return numbers instead. — Barmar
– Barmar, Commented Apr 30, 2014 at 21:02

Cezary Wojcik · Accepted Answer · 2014-04-30 20:57:10Z

3

In JavaScript, "5" + 0 = "50". Make sure your variables are numbers and not strings.

Use the Number() function to be sure.

answered Apr 30, 2014 at 20:57

Cezary Wojcik

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Comments

Grzegorz Adam Kowalski · Accepted Answer · 2014-04-30 21:02:14Z

0

See this input:

var pts_value = 5;
var vat = 5;
var mrp_value = 35;
var quantity = 4;
console.log((mrp_value+(mrp_value*vat/100)-(mrp_value*pts_value/100))*quantity);

var mrp_value = '35';
var quantity = '4';
console.log((mrp_value+(mrp_value*vat/100)-(mrp_value*pts_value/100))*quantity);

This gives this output:

c:\it\nodejs>node.exe 01_hello.js
140
1400

answered Apr 30, 2014 at 21:02

Grzegorz Adam Kowalski

5,6353 gold badges34 silver badges42 bronze badges

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