我这里有一小段代码，它连接到一个名为卡拉 OK 的数据库并填充一个选择框。我只是希望能够在索引 0 处添加一个选择框选项，上面写着“请选择”之类的内容。我尝试了多种方法在 PHP、HTML 和 Javascript 中执行此操作，但尚未找到我需要的解决方案。到目前为止，这段代码在 Chrome 调试器中显示 0 个错误，但并没有按照我的预期运行。有人可以告诉我我做错了什么吗？
<!DOCTYPE HTML>
<html>
<head>
<title>Add Singer</title>
</head>
<body>
<center><label style = "color: white; font-family:arial; font-size: 24px">Select a Regular</label></center>
<?php
$con = mysqli_connect("localhost","root","","karaoke");
// Check connection
if (mysqli_connect_errno())
{
echo "Failed to connect to MySQL: " . mysqli_connect_error();
}
$sql = "Select * FROM regulars ORDER BY Regulars ASC";
$result = mysqli_query($con, $sql) or die("Bad SQL: $sql");
$opt = "<select id = 'regulars' name = 'regulars'>";
while($row = mysqli_fetch_assoc($result)) {
$opt .= "<option value'{$row['Regulars']}'>{$row['Regulars']}</option>\n";
}
$opt .="</select>"
?>
<center> <div id="regulars">
<?php
echo $opt;
?>
</div> </center>
<script>
function myFunction() {
var x = document.getElementById("regulars");
var option = document.createElement("option");
option.text = "Please Select";
x.add(option, x[0]);
}
</sript>
myFunction()
</body>
</html>
最佳答案
您有一个 id="regulars"的 div 标签。该标 checkout 现在打印出包含 select 元素的 $opt 变量之前，该变量也具有 id="regulars"。 Javascript 代码正在查找第一个具有“regulars”id 的元素，即 div。尝试更改 div 的 id。
正如评论中提到的，myFunction函数调用应该在script标签中。 option 标签应包含 = 的 value 属性。
<!DOCTYPE HTML>
<html>
<head>
<title>Add Singer</title>
</head>
<body>
<center><label style = "color: white; font-family:arial; font-size: 24px">Select a Regular</label></center>
<?php
$con = mysqli_connect("localhost","root","","karaoke");
// Check connection
if (mysqli_connect_errno())
{
echo "Failed to connect to MySQL: " . mysqli_connect_error();
}
$sql = "Select * FROM regulars ORDER BY Regulars ASC";
$result = mysqli_query($con, $sql) or die("Bad SQL: $sql");
$opt = "<select id = 'regulars' name = 'regulars'>";
while($row = mysqli_fetch_assoc($result)) {
$opt .= "<option value='{$row['Regulars']}'>{$row['Regulars']}</option>\n";
}
$opt .="</select>"
?>
<center> <div id="regularsDiv">
<?php
echo $opt;
?>
</div> </center>
<script>
function myFunction() {
var x = document.getElementById("regulars");
var option = document.createElement("option");
option.text = "Please Select";
x.add(option, x[0]);
}
myFunction();
</script>
</body>
</html>
关于javascript - 动态创建的选择框不接受功能添加的选项，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/51519238/