在选定下拉列表的两个值之间计算？

Question

如何从两个选定的下拉列表中计算值并显示在文本框中？

而且我想计算汽车不买点击按钮..

HTML代码保险：

<select class="form-control" name="insurance" onchange="calcVals()" id="insurance">

   <option disabled="" selected="" ></option>

   <option value="200">Yes</option>

   <option value="0">No </option>

</select>

人手：

<select class="form-control" name="manpower" id="manpower" onchange="calcVals()">

   <option disabled="" selected=""></option>

   <option value="150">1</option>

   <option value="300">2</option>

   <option value="450">3</option>

   <option value="600">4</option>

   <option value="750">5</option>

</select>

文本框 ：

<input name="totalAmount" id="totalAmount" type="text"  readonly>

javascript:

    function calcVals() {

    var e = document.getElementById("manpower");

    var selFrst = e.options[e.selectedIndex].text;

    var f = document.getElementById("insurance");

    var selScnd = f.options[f.selectedIndex].text;

    var totalCal = selFrst + selScnd;

    document.getElementById("totalAmount").value = totalCal;

 }

Answer 1

首先，添加id="insurance"到保险选择其次，如果要添加值，则需要该值function calcVals() {&nbsp; var e = document.getElementById("manpower");&nbsp; var f = document.getElementById("insurance");&nbsp; var selFrst = e.options[e.selectedIndex].value;&nbsp; var selScnd = f.options[f.selectedIndex].value;&nbsp; var totalCal = +selFrst + +selScnd;&nbsp; document.getElementById("totalAmount").value = totalCal;}<select class="form-control" name="insurance" id="insurance" onchange="calcVals()">&nbsp; <option disabled="" selected=""></option>&nbsp; <option value="200">Yes</option>&nbsp; <option value="0">No </option></select>Manpower:<select class="form-control" name="manpower" id="manpower" onchange="calcVals()">&nbsp; <option disabled="" selected=""></option>&nbsp; <option value="150">1</option>&nbsp; <option value="300">2</option>&nbsp; <option value="450">3</option>&nbsp; <option value="600">4</option>&nbsp; <option value="750">5</option></select>Textbox :<input name="totalAmount" id="totalAmount" type="text" readonly>

Answer 2

尝试在下面你缺少一些东西，我们必须使用 parseInt 将字符串转换为整数。function calcVals() {&nbsp; &nbsp; var e = document.getElementById("manpower");&nbsp; &nbsp; var selFrst = e.options[e.selectedIndex].value;&nbsp; &nbsp; var f = document.getElementById("insurance");&nbsp; &nbsp; var selScnd = f.options[f.selectedIndex].value;&nbsp; &nbsp; var totalCal = parseInt(selFrst) + parseInt(selScnd);&nbsp; &nbsp; document.getElementById("totalAmount").value = totalCal;&nbsp;}<select class="form-control" name="insurance" id="insurance" onchange="calcVals()">&nbsp; &nbsp;<option disabled="" selected="" ></option>&nbsp; &nbsp;<option value="200">Yes</option>&nbsp; &nbsp;<option value="0">No </option></select><select class="form-control" name="manpower" id="manpower" onchange="calcVals()">&nbsp; &nbsp;<option disabled="" selected=""></option>&nbsp; &nbsp;<option value="150">1</option>&nbsp; &nbsp;<option value="300">2</option>&nbsp; &nbsp;<option value="450">3</option>&nbsp; &nbsp;<option value="600">4</option>&nbsp; &nbsp;<option value="750">5</option></select><input name="totalAmount" id="totalAmount" type="text"&nbsp; readonly>

Answer 3

没有 ID“保险”的选择器，因此您必须使用“getElementsByName”而不是 getElementsById。请尝试以下代码：&nbsp;<select class="form-control" name="insurance" id="insurance" onchange="calcVals()">&nbsp; <option disabled="" selected=""></option>&nbsp; <option value="200">Yes</option>&nbsp; <option value="0">No </option></select>Manpower:<select class="form-control" name="manpower" id="manpower" onchange="calcVals()">&nbsp; <option disabled="" selected=""></option>&nbsp; <option value="150">1</option>&nbsp; <option value="300">2</option>&nbsp; <option value="450">3</option>&nbsp; <option value="600">4</option>&nbsp; <option value="750">5</option></select>Textbox :<input name="totalAmount" id="totalAmount" type="text" readonly><script>function calcVals() {&nbsp; &nbsp; var e = document.getElementById("manpower");&nbsp; &nbsp; var selFrst = e[0].value;&nbsp; &nbsp; var f = document.getElementsByName("insurance");&nbsp; &nbsp; var selScnd = f[0].value;&nbsp; &nbsp; var totalCal = parseInt(selFrst) + parseInt(selScnd);&nbsp; &nbsp; document.getElementById("totalAmount").value = totalCal;&nbsp;}</script>