Question

有以下代码：

<html>
<head>
    <script type="text/javascript" src="jquery.js"></script>
</head>
<body>
    <div id="Block"></div>
    <script type="text/javascript">
    function Request(Mode)
    {
        jQuery.ajax
        ({
            url:        "Script.php",
            type:       "POST",
            dataType:   "html",
            data:       "Mode=" + Mode,
            success:    function(responce)
                        {
                            if (responce == '1')
                            {
                                document.getElementById("MessageField").innerHTML = "Message text";
                            }
                            else
                            {
                                document.getElementById("Block").innerHTML = responce;
                            }
                        },
            error:      document.getElementById("Block").innerHTML = "Request error."       
        });
    }
    Request("load form");
    </script>
</body>
</html>

php-script返回html-form或值'1'：

<?php
if ($_POST['Mode'] == 'load form')
    echo
    "
        <form id = 'AuthForm' method = 'post' action = ''>
            <table border = 1>
                <tr>
                    <td id = 'MessageField'>
                        &nbsp
                    </td>
                </tr>
                <tr>
                    <td>
                        <input type = 'submit' name='B1' id='B1' value='Show message' onclick = 'Request()'>
                    </td>
                </tr>
            </table>
        </form>
    ";
else echo "1";
?>

Javascript函数输出html-form或更改其id =“MessageField”的表格单元格的innerHTML。表单显示为假设，但按下按钮我收到错误：

Uncaught TypeError: Cannot set property 'innerHTML' of null

脚本无法执行字符串：

document.getElementById("MessageField").innerHTML = "Message text";

为什么呢？当脚本尝试更改它时，MessageField已存在。 O_O

Answer 1

您指定的代码段中没有任何元素具有ID“Block”

引用动态加载的元素

1 个答案: