Javascript / HTML错误“属性“ selectReason”的值是null或未定义，不是函数对象

Question

Hi I am new to javascript and html and was wondering if someone could help me understand why this error keeps occuring. 嗨，我是javascript和html的新手，想知道是否有人可以帮助我理解为什么此错误不断发生。 The basic idea is that i have a dropdownlist that is populated with several options. 基本思想是我有一个下拉列表，其中填充了多个选项。 When the customer selects an option an onchange event fires that will write the value of the selected option into a textarea. 当客户选择一个选项时，将触发一个onchange事件，该事件会将所选选项的值写入文本区域。 However when i debug it I get the message above I have included the relevant snippets of code below: 但是，当我调试它时，我得到上面的消息，我在下面包含了相关的代码片段：

function selectReason() {
    var selectindex = document.getElementById("selectmessage").selectedIndex;    
    var selecttext = document.getElementById("selectmessage").value;
    document.getElementById("Txt").value = selecttxt;
}

<TR style="DISPLAY: none; VISIBILITY: hidden" id=sel>
    <TD width="60%" align=left>Please select a reason</TD>
    <TD width="40%" align=left>
        <SELECT id="selectmessage" onchange="selectReason()" style="WIDTH: 425px"></SELECT>
    </TD>
</TR>

Answer 1

You might be missing your <table> tags as that was causing a problem for me. 您可能缺少<table>标记，因为这对我造成了问题。 Your provided snippet also has var selecttext and document.getElementById("Txt").value = selecttxt; 您提供的代码段还包含var selecttext和document.getElementById("Txt").value = selecttxt; <- missing an e. <-缺少e。

The provided snippet below works for me. 以下提供的代码段对我有用。 Possibly just failing to close a tag somewhere in your function/html. 可能只是无法在您的function / html中的某个位置关闭标签。

Also (this could be you added inline to provide a better picture) you should avoid inline styles and (to me) functions. 另外（这可能是您添加内联以提供更好的图片），您应该避免使用内联样式和（对我而言）函数。 Include a .css and .js file. 包括一个.css和.js文件。

 function selectReason() { var selectindex = document.getElementById("selectmessage").selectedIndex; var selecttext = document.getElementById("selectmessage").value; var elem = document.getElementById("hey"); elem.innerHTML = selecttext; } // Events to attach function init () { var elem = document.getElementById('selectmessage'); elem.addEventListener('change', selectReason) } // Run 'init' when the DOM is ready (jQuery's $(document).ready() ) document.addEventListener("DOMContentLoaded", init, false);

 <table> <TR> <TD>Please select a reason</TD> <TD> <SELECT id="selectmessage"> <option>Hello</option> <option>Yes</option> </SELECT> </TD> </TR> <tr> <td id='hey'></td> </tr> </table>

Answer 2

Maybe this could help you 也许这可以帮助您

<html>
<head>
    <script src="//ajax.googleapis.com/ajax/libs/jquery/1.11.1/jquery.min.js"></script>
</head>

<body>

    <table>
        <tbody>
            <tr>
                <td>
                    <select name="" id="selectmessage">
                        <option value="red">red</option>
                        <option value="gree">green</option>
                        <option value="blue">blue</option>
                    </select>
                </td>
            </tr>
        </tbody>
    </table>

    <textarea name="" id="txt" cols="30" rows="10">


    </textarea>

    <script type="text/javascript">
        $(document).on('ready', function(){
            $('#selectmessage').on('change', function(){
                var val = $(this).val();

                var txt = $('#txt');

                    txt.val(val);
            });
        });
    </script>

</body>
</html>

hope :) 希望:)

Javascript / HTML错误“属性“ selectReason”的值是null或未定义，不是函数对象

问题描述

2 个解决方案

解决方案1
1 2014-10-30 09:59:31

解决方案2
0 2014-10-30 09:40:15

Javascript / HTML错误“属性“ selectReason”的值是null或未定义，不是函数对象

问题描述

2 个解决方案

解决方案1 1 2014-10-30 09:59:31

解决方案2 0 2014-10-30 09:40:15

解决方案1
1 2014-10-30 09:59:31

解决方案2
0 2014-10-30 09:40:15