为什么我的if语句不能以document.getElementById（“ ID”）。value = var结尾？

Question

I am writing a price checkbox page for my web programming class using javascript where if you check on the boxes and click subtotal, the price is put into a textbox. 我正在使用javascript为我的Web编程类编写一个价格复选框页面，如果您选中这些复选框并单击小计，则价格会放入文本框。 The issue I am having is when I end my if statements with document.getElementById("subtotal").value = total it isn't populating the textbox. 我遇到的问题是当我用document.getElementById("subtotal").value = total结束if语句时，它没有填充文本框。 If I insert an alert or document.write statement then it will populate it. 如果我插入一个alert或document.write语句，那么它将填充它。 Any idea what I am missing? 知道我缺少什么吗？ here is my code with the alerts in place (that I don't want): 这是我的代码，其中有警报（我不想要）：

<!DOCTYPE html>

<head>
    <title> Price Checkbox </title>
    <meta charset = "utf-8" />
    <script>
        var total, a = 0;
    </script>
    <script type = "text/javascript">
        function subtotal1()
        {
            if (document.getElementById('apple').checked)
            {
                total = a + .59;
                a = total;
                document.getElementById("subtotal").value = total
                alert(total);
            }
            if(document.getElementById('orange').checked)
            {
                total = a + .49;
                a = total;
                document.getElementById("subtotal").value = total
                alert(total);
            }
            if(document.getElementById('banana').checked)
            {
                total = a + .39;
                a = total;
                document.getElementById("subtotal").value = total
                alert(total);
            }
        }
    </script>
 </head>
 <body>

     <form id = "myForm"  action = "">
         <p>
            <label> <input type = "checkbox"  id = "apple"/>
            apple $.59 </label>
            <br />
            <label> <input type = "checkbox"  id = "orange"/>
            orange $.49 </label>
            <br />
            <label> <input type = "checkbox"  id = "banana"/>
            banana $.39 </label>
         </p>

         <button onclick = "subtotal1()">Submit</button>
         <p></p>
         <input type="textbox" id="subtotal"/>
     </form>

</body>

Answer 1

I suggest a different approach. 我建议使用另一种方法。 Add an event when the checkbox is clicked. 单击复选框时添加事件。 This way you can also see what is happening and not leave it when submitting the form. 通过这种方式，您还可以查看正在发生的事情，而在提交表单时却不会离开。 Try this code: 试试这个代码：

<body>

     <form id = "myForm"  action = "">
         <p>
            <label> <input type = "checkbox"  id = "apple"  onclick = "subtotal1();"/>
            apple $.59 </label>
            <br />
            <label> <input type = "checkbox"  id = "orange"  onclick = "subtotal1();"/>
            orange $.49 </label>
            <br />
            <label> <input type = "checkbox"  id = "banana"  onclick = "subtotal1();"/>
            banana $.39 </label>
         </p>

         <button>Submit</button>
         <p></p>
         <input type="textbox" id="subtotal"/>
     </form>

</body>

为什么我的if语句不能以document.getElementById（“ ID”）。value = var结尾？

问题描述

1 个解决方案

解决方案1
1 2013-10-20 15:10:40

为什么我的if语句不能以document.getElementById（“ ID”）。value = var结尾？

问题描述

1 个解决方案

解决方案1 1 2013-10-20 15:10:40

解决方案1
1 2013-10-20 15:10:40