使用NaN获取javascript值

Question

我正在努力完成一个在线报价表单的开发。我正在尝试根据复选框是否被勾选来更改价格。

行为应该是:在初始页面加载时-勾选复选框时的标准价格(来自mysql - variable) - ad $20 (来自mysql)到复选框未勾选时的价格-回到标准变量价格

我目前的行为是:在初始页面加载时-勾选复选框时的标准(来自mysql -变量)价格- $20 (来自mysql)，但不会在复选框未勾选时添加到原始价格- NaN

我可以确认价格是以整数形式存储在mysql中的，例如292，任何帮助都将不胜感激。

下面的代码: html页面中的php

<?php 
$table = $_GET['bintype'];
$pcode = $_GET['tags'];
include 'connect.php';
$result=mysqli_query($con,"SELECT * FROM $table WHERE short='$pcode'");
$row_cnt = mysqli_num_rows($result);
if($row_cnt == 0)
{
        PRINT "<p align='middle'>No go</p>"; 
 }
else
while($row=mysqli_fetch_array($result))
  {
  $b = number_format($row['barrow'], 2) AND "<div id='barrowid'>"; 
  $c = number_format($row['2m3 General'], 2) AND "<div id='total_price'>";
  $d = $row['2m3 General'] AND "<div id='total_number'>";

  echo "<form id='checkboxval'><input type='checkbox' id='checkit' name='menu1'
  value=".$b.">
  </input> <div id='total'>Total:$".$d."</div>
  </form>";
  }
mysqli_close($con);
?>

javascript

var checkbox = document.getElementById("checkit");

checkbox.onclick = function () {
    var subtotalField = document.getElementById("total_price");
    var checkboxes = document.forms["checkboxval"].getElementsByTagName("input");
    var subtotal = document.getElementById("total_price");
    var total = document.getElementById("total_price");

 for (var i = 0, length = checkboxes.length; i < length; i++) {
    if (checkboxes[i].checked) {
        var newSubtotal = parseInt(subtotal.innerHTML) + parseInt(checkboxes[i].value);
        subtotal.innerHTML = newSubtotal; 
    }
}

    total = (parseFloat(subtotal));

    document.getElementById("total").innerHTML = "Total:$" + total;
};

Answer 1

您的变量subtotal和total都是DOM元素-您需要在进行运算之前从它们中提取值。

for (var i = 0, length = checkboxes.length; i < length; i++) {
    if (checkboxes[i].checked) {
        var newSubtotal = parseInt(subtotal.innerHTML) + parseInt(checkboxes[i].value);
        subtotal.innerHTML = newSubtotal; 
    }
}

你的代码有点混乱。看一看它，删除冗余和重复的代码。另外，请检查以下内容：document.getElementById("$total_number");。其中是带有id = "$total_number"的元素