JavaScript价格计算错误

Question

Discount Calulation do not output.

(discount is supposed to subtract from Grand Total)

Html

input name="discount" id="discount" type="text">   <button  id="record_button" onclick="recordToFilename();" href="javascript:void(0);" title="Record" > Submit Discount </button>  
     <b id="discount">Discount</b>

Javascript

 function recordTodiscount() {
var input = document.getElementById('discount'),
    discount = input.value;     

check the the jsfiddle click here

document.getElementById('total').innerHTML = "<strong>SubTotal</strong>: $" + salesTotal.toFixed(2); 
document.getElementById('taxtotal').innerHTML = "<strong>Tax </strong>: $" + salesTotal*0.13.toFixed(2);
document.getElementById('grandtotal').innerHTML = "<strong>Grand Total </strong>: $" + salesTotal*0.14 + salesTotal. toFixed(2);//grandtotal and tax total come out the same 
document.getElementById('discount').innerHTML = "<strong>Discount </strong>: $" + salesTotal*0.14 + salesTotal-discount.toFixed(2); //grandtotal and tax total come out the same 

<input name="discount" id="discount" type="number">

Answer 1

The period operator has higher precedence than the mathematical operators, so the toFixed method will be applied before the addition. As that makes the second operand a string, the + operator will do string concatenation instead of addition.

You need parentheses to make the calculations happen before the toFixed call:

(salesTotal * 0.13).toFixed(2)

(salesTotal * 0.14 + salesTotal).toFixed(2)

(salesTotal * 0.14 + salesTotal - discount).toFixed(2)

You are using 0.13 when calculating the tax, and 0.14 when calculating the total, they should probably be the same.

Instead of adding the total and the tax, you can just add one to the constant that you are multiplying with, ie salesTotal * 0.14 + salesTotal is the same as salesTotal * 1.14 .