Javascript 使用onchange选择下拉列表值_Javascript_Php_Html_Drop Down Menu

Javascript 使用onchange选择下拉列表值

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Javascript 使用onchange选择下拉列表值,javascript,php,html,drop-down-menu,Javascript,Php,Html,Drop Down Menu,你能告诉我我做错了什么吗。我正在尝试选择新的下拉列表值。我试图通过调用一个alert函数来验证我是否已经gopt了新值，该函数的值输出为未定义，但我能够很好地选择id。代码如下： <?php require'includes/opendb.php'; $DNS = $_GET['DNS'] ?> <html> <head> </head> <body> <p>

你能告诉我我做错了什么吗。我正在尝试选择新的下拉列表值。我试图通过调用一个alert函数来验证我是否已经gopt了新值，该函数的值输出为未定义，但我能够很好地选择id。代码如下：

<?php
    require'includes/opendb.php';
    $DNS = $_GET['DNS']
?>
<html>
    <head>

    </head>

    <body>
        <p>
            This section allows you to connect Uplink ports to different switches. Be sure that all the information is correct before you submit.
        </p>
        <form action="" method="post" enctype = "multipart/form-data">
            <table border = 1>
                <tr>
                    <td>DNS From</td>
                    <td>DNS To</td>
                </tr>
                    <?php
                        $DNS_FROM = $DNS."_port-%";
                        $select = "SELECT * FROM `uplink_port_mapping` WHERE DNS_From LIKE '$DNS_FROM'";
                        $select1 = mysqli_query($conn, $select);
                        $select2 = "SELECT DNS_From FROM `uplink_port_mapping` WHERE DNS_From NOT LIKE '$DNS_FROM' AND DNS_To = ''";
                        $select3 = mysqli_query($conn, $select2);
                        $i = 0;
                        while($uplink_from = mysqli_fetch_assoc($select1)){
                            echo "<tr>";
                                echo "<td>".$uplink_from['DNS_From']."</td>";
                                echo "<td>"."<select name = 'uplink_to_".$i."' id = 'uplink_to_".$i."' Onchange = 'dropdown(this)'> 
                                    <option value = '".$uplink_from['DNS_To']."' selected='selected'>". $uplink_from['DNS_To']."</option>";

                                mysqli_data_seek($select3, 0);

                                while($uplink_to = mysqli_fetch_assoc($select3)){
                                    echo "<option value='".$uplink_to['DNS_From']."'>".$uplink_to['DNS_From']."</option>";
                                }
                                echo"</select>";
                                echo"</td>";
                            echo"</tr>";
                            ++$i;
                        }
                    ?>
            </table>
        </form>
    </body>
</html>
<script>
    function dropdown(checkbox){
        var id = checkbox.id;
        var value = checkbox.val;
        alert("You have changed "+id+" to "+value)
    }
</script>



本节允许您将上行链路端口连接到不同的交换机。提交前请确保所有信息正确无误。

DNS来自
DNS到
功能下拉列表（复选框）{
var id=checkbox.id；
var值=checkbox.val；
警报（“您已将“+id+”更改为“+value”）
}

来自CHROME源代码的HTML版本

<html>
    <head>

    </head>

    <body>
        <p>
            This section allows you to connect Uplink ports to different switches. Be sure that all the information is correct before you submit.
        </p>
        <form action="" method="post" enctype = "multipart/form-data">
            <table border = 1>
                <tr>
                    <td>DNS From</td>
                    <td>DNS To</td>
                </tr>
                    <tr><td>HEPSAN02_port-00</td><td><select name = 'uplink_to_0' id = 'uplink_to_0' Onchange = 'dropdown(this)'> 
                                    <option value = 'HEPSAN5_port-00' selected='selected'>HEPSAN5_port-00</option><option value='HEPSAN03_port-24'>HEPSAN03_port-24</option><option value='HEPSAN1_port-01'>HEPSAN1_port-01</option><option value='HEPSAN1_port-02'>HEPSAN1_port-02</option><option value='HEPSAN4_port-18'>HEPSAN4_port-18</option><option value='HEPSAN4_port-19'>HEPSAN4_port-19</option></select></td></tr><tr><td>HEPSAN02_port-01</td><td><select name = 'uplink_to_1' id = 'uplink_to_1' Onchange = 'dropdown(this)'> 
                                    <option value = 'HEPSAN5_port-01' selected='selected'>HEPSAN5_port-01</option><option value='HEPSAN03_port-24'>HEPSAN03_port-24</option><option value='HEPSAN1_port-01'>HEPSAN1_port-01</option><option value='HEPSAN1_port-02'>HEPSAN1_port-02</option><option value='HEPSAN4_port-18'>HEPSAN4_port-18</option><option value='HEPSAN4_port-19'>HEPSAN4_port-19</option></select></td></tr><tr><td>HEPSAN02_port-02</td><td><select name = 'uplink_to_2' id = 'uplink_to_2' Onchange = 'dropdown(this)'> 
                                    <option value = '' selected='selected'></option><option value='HEPSAN03_port-24'>HEPSAN03_port-24</option><option value='HEPSAN1_port-01'>HEPSAN1_port-01</option><option value='HEPSAN1_port-02'>HEPSAN1_port-02</option><option value='HEPSAN4_port-18'>HEPSAN4_port-18</option><option value='HEPSAN4_port-19'>HEPSAN4_port-19</option></select></td></tr>           </table>
        </form>
    </body>
</html>
<script>
    function dropdown(checkbox){
        var id = checkbox.id;
        var value = checkbox.val;
        alert("You have changed "+id+" to "+value)
    }
</script>



本节允许您将上行链路端口连接到不同的交换机。提交前请确保所有信息正确无误。

DNS来自
DNS到
HEPSAN02_端口-00
HEPSAN5_端口-00HEPSAN03_端口-24HEPSAN1_端口-01HEPSAN1_端口-02HEPSAN4_端口-18HEPSAN4_端口-19HEPSAN02_端口-01
HEPSAN5_端口-01HEPSAN03_端口-24HEPSAN1_端口-01HEPSAN1_端口-02HEPSAN4_端口-18HEPSAN4_端口-19HEPSAN02_端口-02
HEPSAN03_端口-24HEPSAN1_端口-01HEPSAN1_端口-02HEPSAN4_端口-18HEPSAN4_端口-19
功能下拉列表（复选框）{
var id=checkbox.id；
var值=checkbox.val；
警报（“您已将“+id+”更改为“+value”）
}

感谢您的帮助：）

所做的更改
► <代码>变量值=checkbox.val至
var value=checkbox.value 工作演示函数下拉列表（复选框）{ var id=checkbox.id； var值=checkbox.value；警报（“您已将“+id+”更改为“+value”） } 本节允许您将上行链路端口连接到不同的交换机。提交前请确保所有信息正确无误。 DNS来自 DNS到 HEPSAN02_端口-00 HEPSAN5_端口-00 HEPSAN03_端口-24 HEPSAN1\U端口-01 HEPSAN1_端口-02 赫普桑4_港-18 赫普桑4_港-19 HEPSAN02\U端口-01 HEPSAN5_端口-01 HEPSAN03_端口-24 HEPSAN1\U端口-01 HEPSAN1_端口-02 赫普桑4_港-18 赫普桑4_港-19 HEPSAN02\U端口-02 HEPSAN03_端口-24 HEPSAN1\U端口-01 HEPSAN1_端口-02 赫普桑4_港-18 赫普桑4_港-19 为什么要包含jQuery？@jeff创建代码片段是一种习惯。谢谢你指出这一点。我将编辑我的answer@RinoRaj是啊就这么做了。。谢谢（顺便说一句：）