如何添加一些值然后使用jquery减去它们

Question

我从输入框中的数据库中获取值，然后添加值。有一些输入字段可以扣除这些值;我已经编写了代码，但它没有工作，它只给了我总和值，但没有做减法。请帮助我。

＆＃13;

＆＃13;

<script type ="text/javascript">
	
	$(document).ready(function(){
 
        //iterate through each textboxes and add keyup
        //handler to trigger sum event
        $(".text").each(function() {
 
            $(this).on('input',function(){
                calculateSum();
            });
        });
    
        // call calculateSum function after typing in subtract field
        $('.sub').on('input',calculateSum);
 
    });

    // function for subtracting from total
    function totalSubtract(sumTotal) {
     
      var subtract = parseFloat($('.sub').val());
         sumTotal -= subtract;
         return sumTotal;
    }
 
    function calculateSum() {
 
        //console.log('calc');
        
        var total = 0;
        //iterate through each textboxes and add the values
        $(".text").each(function() {
 
            //add only if the value is number
            if(!isNaN(this.value) && this.value.length!=0) {
                total += parseFloat(this.value);
            }
        });
        
        // subtract from total
        total = totalSubtract(total);
        
        //.toFixed() method will roundoff the final sum to 2 decimal places
        $("#amount").val(total.toFixed(2));
    }
	 
    </script>

＆＃13;

＆＃13;

＆＃13;