HTML 表單輸入 javascript autosum 總價支付

Question

我有以下代碼來銷售產品，如果我應用折扣，它會起作用，如果我應用稅收，則相同，每單位的所有價格（數量 1）都有效，但是如果我改變數量，則支付的總價無效

我需要的是自動填充以稍后將以下字段保存到 mysql：

default price per unit (comming from mysql) = working
apply taxes or not per unit = working
apply discount per unit = working
price per unit after discount and after taxes = working

如果我將數量從 1 更改為 2 o 3 等，要支付的總價 = 不起作用 這必須通過乘數自動填充以按數量計算每單位稅后支付 = 不起作用

這是代碼

<table width="339" border="0" cellpadding="0">
  <tr>
    <td width="98">Pay taxes?</td>
    <td width="115">Make Discount?</td>
    <td width="118">Default unit price</td>
     <td>Quantity</td>
  </tr>
  <tr>
    <td>
      <select name="taxes" class="select">
        <option value="0" selected>no taxes</option>
        <option value="19">19% taxes</option>
      </select>
    </td>
    <td>
      <select name="discount" class="select">
        <option value="0" selected>no discount</option>
        <option value="5">5% discount</option>
        <option value="10">10% discount</option>
        <option value="20">20% discount</option>
      </select>
    </td>
    <td>
      <input type="text" name="cost" class="input140" value="1000">
    </td>
    <td><input type="text" name="quantity" value="1"></td>
  </tr>
  <tr>
    <td>Unit price after discount</td>
    <td>Tax per unit</td>
    <td>Total Price per unit</td>
     <td>Total Price to pay per quantity</td>
  </tr>
  <tr>
    <td><input type="text" name="price" value="1000"></td>
    <td><input type="text" name="ttaxes" value="0"></td>
    <td><input type="text" name="total" value="1000"></td>
    <td><input type="text" name="totaltopay" value="1000"></td>
  </tr>
 </table><script>
/**
 * Elements
 */
var taxes    = document.getElementsByName('taxes')[0];
var discount = document.getElementsByName('discount')[0];
var cost     = document.getElementsByName('cost')[0];
var price    = document.getElementsByName('price')[0];
var ttaxes   = document.getElementsByName('ttaxes')[0];
var total    = document.getElementsByName('total')[0];


/**
 * Calculations
 */
function updateInput() {
  price.value = cost.value - (cost.value * (discount.value / 100));
  ttaxes.value = (price.value * (taxes.value / 100));
  var sum = parseFloat(price.value) + parseFloat(ttaxes.value);
  total.value = sum.toFixed(0);
}


/**
 * Event Listeners
 */
taxes.addEventListener('change', updateInput);
discount.addEventListener('change', updateInput);
cost.addEventListener('change', updateInput);
cost.addEventListener('keyup', updateInput);
</script>

這是演示小提琴

https://fiddle.jshell.net/63dkvgs5/

我需要的圖像示例

Answer 1

你忘記加數量了！

var quantity = document.getElementsByName('quantity')[0];
quantity.addEventListener('keyup', updateInput);

並更新計算：

var sum = (parseFloat(price.value) + parseFloat(ttaxes.value)) * quantity.value;

小提琴： https : //fiddle.jshell.net/praveenscience/v6spxoqv/

Answer 2

<table width="339" border="0" cellpadding="0">
  <tr>
    <td width="98">Pay taxes?</td>
    <td width="115">Make Discount?</td>
    <td width="118">Default unit price</td>
     <td>Quantity</td>
  </tr>
  <tr>
    <td>
   <select name="taxes" class="select">
    <option value="0" selected>no taxes</option>
    <option value="5">5% taxes</option>
    <option value="10">10% taxes</option>
    <option value="20">20% taxes</option>
    <option value="27">27% taxes</option>
    <option value="30">30% taxes</option>
    <option value="40">40% taxes</option>
    <option value="50">50% taxes</option>
   </select>
    </td>
    <td>
   <select name="discount" class="select">
    <option value="0" selected>no discount</option>
    <option value="5">5% discount</option>
    <option value="10">10% discount</option>
    <option value="20">20% discount</option>
   </select>
    </td>
    <td>
     <input type="text" name="cost" class="input140" value="100">
    </td>
    <td><input type="text" name="quantity" value="1"></td>
  </tr>
  <tr>
    <td>Unit price after discount</td>
    <td>Tax per unit</td>
    <td>Total Price per unit</td>
     <td>Végösszeg Total Price to pay per quantity</td>
  </tr>
  <tr>
    <td><input type="text" name="price" value="100"></td>
    <td><input type="text" name="ttaxes" value="0"></td>
    <td><input type="text" name="total" value="100"></td>
    <td><input type="text" name="totaltopay" value="100"></td>
  </tr>
 </table>
<script>
/* Elements */
var taxes    = document.getElementsByName('taxes')[0];
var discount = document.getElementsByName('discount')[0];
var cost     = document.getElementsByName('cost')[0];
var price    = document.getElementsByName('price')[0];
var ttaxes   = document.getElementsByName('ttaxes')[0];
var total    = document.getElementsByName('total')[0];
var totaltopay = document.getElementsByName('totaltopay')[0];
var quantity = document.getElementsByName('quantity')[0];
quantity.addEventListener('keyup', updateInput);
/* Calculations */
function updateInput() {
  price.value = cost.value - (cost.value * (discount.value / 100));
  ttaxes.value = (price.value * (taxes.value / 100));
  totaltopay.value = (price.value * quantity.value) + (taxes.value * quantity.value);
  var sum = parseFloat(price.value) + parseFloat(ttaxes.value);
  total.value = sum.toFixed(0);
  var sum = (parseFloat(price.value) + parseFloat(ttaxes.value)) * quantity.value;
}
/* Event Listeners */
taxes.addEventListener('change', updateInput);
discount.addEventListener('change', updateInput);
cost.addEventListener('change', updateInput);
cost.addEventListener('keyup', updateInput);
</script>