JavaScript 算术返回意外值

Question

这是一个简单的 JS 片段，

$("#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);
        }
    }); 
});

我通过 JSON AJAX 请求获得的值是，

{"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}

如果我单独打印值，它会显示，

var mrp_value = 35;
var quantity = 4;

赋值是， 变量 pts_value = 5; 变量增值税 = 5;

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

所以，我希望这会按如下方式执行，

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

但它返回 1400 作为值。我为什么以及在哪里犯了错误？

Answer 1

在 JavaScript 中，“5”+ 0 =“50”。确保您的变量是数字而不是字符串。

使用 Number()确保功能。