javascript - 如何在网页中添加文本框验证？

Question

嗨，我有两个文本框。一张用于用户名，另一张用于密码。目前，如果任何字段留空，我有用于显示错误消息“无效凭据”的代码。这会将我带到显示错误消息的新页面，并将我带回到主页，我可以在其中再次输入我的用户名和密码。

我希望验证部分在文本框本身附近完成。例如，如果“用户名”文本框留空并单击“提交”按钮，则应显示一条消息，例如“请在文本框本身附近输入用户名”。

HTML 代码:

<form method="post" action="login.php">
      <p class="user_text">USER LOGIN</p>
      <p class="user_name_text">username<span style="color:#f60219;"> *</span></p>
      <p style="padding:8px 0 0 5px;">

        <input type="text" name="username" minlength="2" maxlength="20" class="contact_filed" value="enter your name" onfocus="javascript:clearField(this,'enter your name')" onblur="javacript:fillField(this,'enter your name')" /></label>
     </p>
      <p class="user_name_text1">password<span style="color:#f60219;"> *</span></p>
      <p style="padding:8px 0 0 5px;">
        <input type="password" name="password" maxlength="20" class="contact_filed" value="password" onfocus="javascript:clearField(this,'password')" onblur="javacript:fillField(this,'password')" />
      </p>
      <p style="padding:16px 0 0 16px;"><input name="submit" type="submit" value="Submit" class="log" /></p>
      <p style="padding:12px 0 0 16px;"><a href="#" class="read_more1">Create new account</a><a href="#" class="read_more1">Request new password</a></p>
</form>

用于验证的 PHP 代码:

if ($_POST['submit']) { 
include('connect.php'); 
$u = mysql_real_escape_string($_POST['username']); 
$p = md5($_POST['password']); 
$q = mysql_query("SELECT id FROM $login_db_table WHERE username='$u' AND password='$p' LIMIT 1"); 

if (mysql_fetch_array($q, MYSQL_ASSOC)) { 
    if ($_POST['remember']) { 
        setcookie('username', $_POST['username'], time() + 5000000); 
        setcookie('password', md5($_POST['password']), time() + 5000000); 
    } else { 
        setcookie('username', $_POST['username']); 
        setcookie('password', md5($_POST['password'])); 
    } 


if($u != "" && $p !=""){
echo '<p>Login successful.</p>'; 
header("Location: main.php");
}

} 

else
echo "Login failed. Please enter valid credentials.";
echo "<script>setTimeout(\"location.href = 'http://localhost/CashTree/reg/Home/index.html';\",1500);</script>";
    //echo '<p>Login failed. Please enter your correct credentials</p>'; 

} 

Answer 1

您可以在元素 say 附近添加一个 html 元素

    <p style="padding:8px 0 0 5px;">

        <input id="uname" type="text" name="username" minlength="2" maxlength="20" class="contact_filed" value="enter your name" onfocus="javascript:clearField(this,'enter your name')" onblur="javacript:fillField(this,'enter your name')" />
<div id="user_name_invalid"></div>
     </p>

然后

使用 jQuery

<script type='text-javascript'>
 $("#form").submit(function(e){
   var uname = $("#username").val();
   if(uname == ""){
     $("#user_name_invalid").html("Username is invalid");
     return false;
   }
}
</script>

return false; 停止提交。