javascript - js 不工作时返回 false

Question

这个问题已经有答案了:

problem with javascript: return false is not working (6 个回答)

已关闭 7 年前。

我知道这个问题已经被问过很多次了，但我很难理解为什么 return false在我的代码中不起作用。我期望当用户将字段留空时，JS 应该停止表单发布。这是我的代码:

HTML:

<form name="MyForm" method="post" action="">
<div class="span-5">
<label>Select Class</label>
<div>
<select name="selectclass" id="selectclass">
<option value="none">-Select Class-</option>
<?php while($class=mysqli_fetch_array($fetchclass)) 
{ ?>                    
<option value="<?php echo $class['class_name'];?>"
<?php if(isset($_POST['selectclass'])) { if(!strcmp($_POST['selectclass'],$class['class_name'])) echo "selected"; }?>
><?php echo $class['class_name'];?></option>
<?php }?>                    
</select>
</div>
</div>
<div class="span-5">
        <label>Select View</label>
        <div>
            <select name="selectview" id="selectview">
            <option value="none">-Select-</option>
            <option value="chapter" <?php if(isset($_POST['selectview'])) { if(!strcmp($_POST['selectview'],"chapter")) echo "selected"; }?>>View Chapters</option>
            <option value="topic" <?php if(isset($_POST['selectview'])) { if(!strcmp($_POST['selectview'],"topic")) echo "selected"; }?>>View Topics</option>
            <option value="lecture" <?php if(isset($_POST['selectview'])) { if(!strcmp($_POST['selectview'],"lecture")) echo "selected"; }?>>View Lectures</option>
            <option value="assignment" <?php if(isset($_POST['selectview'])) { if(!strcmp($_POST['selectview'],"assignment")) echo "selected"; }?>>View Assignment</option>
            <option value="evaluationtest" <?php if(isset($_POST['selectview'])) { if(!strcmp($_POST['selectview'],"evaluationtest")) echo "selected"; }?>>View Evaluation Test</option>
            <option value="exampaper" <?php if(isset($_POST['selectview'])) { if(!strcmp($_POST['selectview'],"exampaper")) echo "selected"; }?>>View ExamPapers</option>
            </select>
        </div>
        </div>
<div>
    <input type="submit" value="View" onclick="checkview()" name="btn" class="blue-btn" />
    </div>
    </div>
</form>

这是我的 JS:

<script type="text/javascript">
function checkview()
{
    var classname1 = $('#selectclass').val();
    var select_view = $('#selectview').val();
    if (classname1 == 'none' || select_view == 'none')
        {
            alert('Please fill all fields!!');
            return false;
        };
}
</script>

当我发布此表单时，它会向我显示警报(未选择任何选项)，然后我希望它不会被发布，但它会被发布。我找不到阻止此表单发布的方法!!

P.S.我第一次在这里问问题。所以请不要介意我的愚蠢错误。
提前致谢!

Answer 1

将其作为返回

 <form name="MyForm" method="post" action="" onsubmit="return checkview() ">

最后将其设为

 <input type="submit" value="View"  name="btn" class="blue-btn" />

onsubmit 是一个 js 事件，在提交表单时调用，并根据 bool 值不提交或提交