脚本 - 对总和值

Question

单个选定项目的总和正在运行，但我不知道如何连接＆＃34;默认价格＆＃34; （我用于演示）到＆＃34; Total＆＃34;其余的计算（税收和折扣）。

＆＃13;

＆＃13;

function chaked1() {
  $("#filled-in-box1").click(function(event) {
    if (this.checked) {
      document.getElementById("one").value = document.getElementById("filled-in-box1").value;
      document.getElementById('one').readOnly = false;
    } else {
      document.getElementById("one").value = "0";
      document.getElementById('one').readOnly = true;
    }

  });
}

function chaked2() {
  $("#filled-in-box2").click(function(event) {
    if (this.checked) {
      document.getElementById("two").value = document.getElementById("filled-in-box2").value;
      document.getElementById('two').readOnly = false;
    } else {
      document.getElementById("two").value = "0";
      document.getElementById('two').readOnly = true;
    }
  });

}
$(".tot_amount").click(function(event) {
  var total = 0;
  $(".tot_amount:checked").each(function() {
    total += parseInt($(this).val());
  });

  if (total == 0) {
    $('#cost').val('');
  } else {
    $('#cost').val(total);
  }
});


function updateInput() {
  var discount = document.getElementsByName("discount")[0].value;
  var cost = document.getElementsByName("cost")[0].value;
  document.getElementsByName("price")[0].value = cost - (cost * (discount / 100));

  var taxes = document.getElementsByName("taxes")[0].value; // <======================
  if (isNaN(taxes)) // IF "no taxes" IS SELECTED...
    document.getElementsByName("ttaxes")[0].value = 0;
  else {
    cost = document.getElementsByName("price")[0].value;
    document.getElementsByName("ttaxes")[0].value = (cost * (taxes / 100));
  }
}

＆＃13;

<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<table>
  <tr>
    <td>
      <input type="checkbox" class="tot_amount" value="10" id="filled-in-box1" onclick="chaked1();">10
    </td>
  </tr>
  <tr>
    <td>
      <input type="checkbox" class="tot_amount" value="20" id="filled-in-box1" onclick="chaked1();">20
    </td>
  </tr>
  <tr>
    <td>
      <input type="checkbox" class="tot_amount" value="30" id="filled-in-box1" onclick="chaked1();">30
    </td>
  </tr>
  <tr></tr>
  <tr>
    <td>Total
      <input type="text" id="cost" readonly>
    </td>
  </tr>
  <tr>
    <td width="98">Taxes</td>
    <td width="115">Discount</td>
    <td width="118">Default price</td>
  </tr>
  <tr>
    <td>
      <select class="select" name="taxes" onChange="updateInput()">
        <option value="no" selected>no taxes</option>
        <option value="19">19% taxes</option>
        <!-- <====================== -->
      </select>
    </td>
    <td>
      <select class="select" name="discount" onChange="updateInput()">
        <option value="0" selected>0% 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" class="select" name="cost" id="cost" value="1000">
    </td>
  </tr>
  <tr>
    <td>Price after discount</td>
    <td>Taxes</td>
    <td>&nbsp;</td>
  </tr>
  <tr>
    <td>
      <input type="text" name="price" value="0">
    </td>
    <td>
      <input type="text" name="ttaxes" value="0">
    </td>
    <!-- <====================== -->
  </tr>
</table>

＆＃13;

＆＃13;

＆＃13;