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HTML
<!DOCTYPE html>
<html>
<head>
  <meta charset="utf-8">
  <meta name="viewport" content="width=device-width">
  <title>文本框 - 表单验证</title>
  <link rel="stylesheet" href="https://cdn.w3cbus.com/library/mdui/1.0.2/css/mdui.min.css"/>
</head>
<body>

  <div class="mdui-container">
    <div class="mdui-textfield mdui-textfield-floating-label">
      <label class="mdui-textfield-label">User name</label>
      <input class="mdui-textfield-input" type="text" required/>
      <div class="mdui-textfield-error">用户名不能为空</div>
    </div>

    <div class="mdui-textfield mdui-textfield-floating-label">
      <label class="mdui-textfield-label">Email</label>
      <input class="mdui-textfield-input" type="email" required/>
      <div class="mdui-textfield-error">邮箱格式错误</div>
    </div>

    <div class="mdui-textfield mdui-textfield-floating-label">
      <label class="mdui-textfield-label">Password</label>
      <input class="mdui-textfield-input" type="text" pattern="^.*(?=.{6,})(?=.*[a-z])(?=.*[A-Z]).*$" required/>
      <div class="mdui-textfield-error">密码至少 6 位，且包含大小写字母</div>
      <div class="mdui-textfield-helper">请输入至少 6 位，且包含大小写字母的密码</div>
    </div>
  </div>

  <script src="https://cdn.w3cbus.com/library/mdui/1.0.2/js/mdui.min.js"></script>
</body>
</html>
CSS

  

  

    
JavaScript