根据用户html-select输出一个字符串

Question

我有一个表单，用户输入1到10的数量，以及一个只读文本字段，我需要输出一个计算价格的字符串。也可能是容器的另一个王者，但由于位置在格式化的单元格内，我宁愿不使用div。如上所述，任何内容都在一个表单中，用于将值（也有验证码）发布到购买过程的php文件中。就我而言，这是我的代码：

function calculatePrice() {
  var form = document.getElementById('buy_form');
  var num_pieces = parseInt(form.elements.number_select.value);
  var price_for_1 = 9.90; //I know, hardcoded is worst, I'll take it from the DB later on
  var totalprice = price_for_1 * num_pieces;
  document.getElementById("total_price").innerHTML = "Total price: \u20AC " + totalprice;
}

<form method="post" id="buy_form" action="buy.php">

<select name="numberselect" id="number_select" onChange="calculatePrice()">
<option value="1">1</option>
<option value="2">2</option>
<option value="3">3</option>
<option value="4">4</option>
<option value="5">5</option>
<option value="6">6</option>
<option value="7">7</option>
<option value="8">8</option>
<option value="9">9</option>
<option value="10">10</option>
</select>

<input type=text class="totalprice" id="total_price" style="border: none" readonly>

//a captcha image
//a captcha input field
//a submit button

</form>

该函数不会在只读文本字段中输出任何内容。我错过了什么？

Answer 1

document.getElementById("total_price").innerHTML 

应该，

document.getElementById("total_price").value

function calculatePrice() {
        var form = document.getElementById('buy_form');
        var num_pieces = parseInt(form.elements.number_select.value);
        var price_for_1 = 9.90; //I know, hardcoded is worst, I'll take it from the DB later on
        var totalprice = price_for_1 * num_pieces;
        document.getElementById("total_price").value = "Total price: \u20AC " + totalprice;
    }

<form method="post" id="buy_form" action="buy.php">

    <select name="numberselect" id="number_select" onChange="calculatePrice()">
        <option value="1">1</option>
        <option value="2">2</option>
        <option value="3">3</option>
        <option value="4">4</option>
        <option value="5">5</option>
        <option value="6">6</option>
        <option value="7">7</option>
        <option value="8">8</option>
    </select>

    <input type=text class="totalprice" id="total_price" style="border: none" readonly>
</form>

Answer 2

实际问题是

 document.getElementById("total_price").innerHTML

innerHTML将永远不会工作，因为innerHTML将在javascript中提取的元素上添加HTML元素

应该用，

document.getElementById("total_price").value

所以功能看起来像这样

function calculatePrice() { 
  var form = document.getElementById('buy_form');
  var num_pieces = parseInt(form.elements.number_select.value);
  var price_for_1 = 9.90; //I know, hardcoded is worst, I'll take it from the DB later on
  var totalprice = price_for_1 * num_pieces;
  document.getElementById("total_price").value = "Total price: \u20AC " + totalprice;
}

希望这会有所帮助

Answer 3

在您的JavaScript代码中，请执行以下更改：

function calculatePrice() {
  var form = document.getElementById('buy_form');
  var num_pieces = parseInt(form.elements.number_select.value);
  var price_for_1 = 9.90; //I know, hardcoded is worst, I'll take it from the DB later on
  var totalprice = price_for_1 * num_pieces;
  document.getElementById("total_price").value = "Total price: \u20AC " + totalprice;
}

window.calculatePrice = calculatePrice;

1. 将innerHTML更改为value。
2. 将该函数添加到window对象。

Answer 4

这可能是你想念的小事。如果这是本机HTML和JS，则事件是onchange，而不是onChange

试试这个！