Javascript 未捕获类型错误：无法读取属性'；innerHTML'；空ajaxjquery的实现

我试着用ajax做即时评论，我得到了一个错误，说UncaughtTypeError:Cannotreadproperty'innerHTML'为null，我无法修复它，有人能帮我修复吗？我在学习教程（）

函数sendPost（）{
var comment=document.getElementById（“comment”）.value；
var name=document.getElementById（“用户名”）.value；
if（注释和名称）{
$.ajax
({
键入：“POST”，
url:“post_comments.php”，
数据：{
用户通信：评论，
用户名：name
},
成功：功能（响应）{
控制台日志（响应）；
document.getElementById（“commentList”）.innerHTML=response+document.getElementById（“commentList”）.innerHTML；
document.getElementById（“注释”）.value=“”；
document.getElementById（“用户名”）.value=“”；
}
});
}
返回false；
}

这是我显示评论的索引页

                            <?php
                                $servername = "localhost";
                                $username = "root";
                                $password = "";

                                // Create connection
                                $con = new mysqli($servername, $username, $password);
                                $db = mysqli_select_db($con,"Review");
                                $qry = mysqli_query($con,"select name,comment,post_time from comments order by post_time desc");
                            while($row=mysqli_fetch_array($qry))
                            {
                              $name=$row['name'];
                              $comment=$row['comment'];
                              $time=$row['post_time'];
                        ?>


<div class="detailBox" id="detailBox">
    <div class="titleBox">
      <label>Comment Box</label>
        <button type="button" class="close" aria-hidden="true">&times;</button>
    </div>
    <div class="commentBox">

        <p class="taskDescription">test</p>
    </div>
    <div class="actionBox" id="actionBox">
        <ul class="commentList" id="commentList">
            <li>
                <div class="commenterImage">
                  <p><?php echo $name;?>:</p>
                </div>
                <div class="commentText">
                    <p class=""><?php echo $comment;?></p> <span class="date sub-text">on <?php echo $time;?></span>
                </div>

            </li>
        </ul>
        <?php
         }
        ?>
       <form class="form-inline" role="form" method="post" onsubmit="return sendPost();">
            <div class="row">
                <div class="col-md-12">
                    <div class="form-group">
                        <input class="form-control" type="text" placeholder="Your name" / required="" id="username">
                    </div>
                </div>
            </div>
            <div class="row">
                <div class="col-md-12">
                    <div class="form-group">
                        <textarea class="form-control" id="comment" placeholder="your comments....." required=""></textarea>
                    </div>
                </div>
            </div>
            <br>
            <div class="form-group">
                <input class="btn btn-default" type="submit" value="Submit">
            </div>
        </form>
    </div>
</div>

评论框
&时代；
测试



:

打开

请发布您的HTML.is

document.getElementById（“commentList”）

实际找到了吗？如何在注释中添加代码？在教程中，我看到document.getElementById（“所有注释”）.innerHTML=response+document.getElementById（“所有注释”）.innerHTML@Sazny14您不能将innerHtml（）与UL标记一起使用，请尝试附加LI或替代函数，您提到的教程使用div标记添加注释，但您使用的是UL LI标记请发布您的HTML.is

document.getElementById（“commentList”）

实际找到？如何在注释中添加代码？在教程中，我看到document.getElementById（“所有注释”）.innerHTML=response+document.getElementById（“所有注释”）.innerHTML@Sazny14您不能将innerHtml（）与UL标记一起使用，请尝试附加LI或alternate函数，您提到的教程使用div标记添加注释，但您使用的是UL LI标记

                            <?php
                                $servername = "localhost";
                                $username = "root";
                                $password = "";

                                // Create connection
                                $con = new mysqli($servername, $username, $password);
                                $db = mysqli_select_db($con,"Review");
                                $qry = mysqli_query($con,"select name,comment,post_time from comments order by post_time desc");
                            while($row=mysqli_fetch_array($qry))
                            {
                              $name=$row['name'];
                              $comment=$row['comment'];
                              $time=$row['post_time'];
                        ?>


<div class="detailBox" id="detailBox">
    <div class="titleBox">
      <label>Comment Box</label>
        <button type="button" class="close" aria-hidden="true">&times;</button>
    </div>
    <div class="commentBox">

        <p class="taskDescription">test</p>
    </div>
    <div class="actionBox" id="actionBox">
        <ul class="commentList" id="commentList">
            <li>
                <div class="commenterImage">
                  <p><?php echo $name;?>:</p>
                </div>
                <div class="commentText">
                    <p class=""><?php echo $comment;?></p> <span class="date sub-text">on <?php echo $time;?></span>
                </div>

            </li>
        </ul>
        <?php
         }
        ?>
       <form class="form-inline" role="form" method="post" onsubmit="return sendPost();">
            <div class="row">
                <div class="col-md-12">
                    <div class="form-group">
                        <input class="form-control" type="text" placeholder="Your name" / required="" id="username">
                    </div>
                </div>
            </div>
            <div class="row">
                <div class="col-md-12">
                    <div class="form-group">
                        <textarea class="form-control" id="comment" placeholder="your comments....." required=""></textarea>
                    </div>
                </div>
            </div>
            <br>
            <div class="form-group">
                <input class="btn btn-default" type="submit" value="Submit">
            </div>
        </form>
    </div>
</div>