01.<!DOCTYPE html>
02.<html>
03.<head>
04.<meta content="width=device-width initial-scale=1.0 minimum-scale=1.0 maximum-scale=1.0 user-scalable=no" name="viewport">
05.<meta charset="UTF-8">
06.<link rel="stylesheet" href="https://cdnjs.cloudflare.com/ajax/libs/twitter-bootstrap/4.1.1/css/bootstrap.css">
07.
08.<style>
09.</style>
10.
11.<script>
12.</script>
13.
14.</head>
15.<body>
16.<div class="alert alert-primary">
17.正規表現で入力チェック( required は必須入力 )
18.</div>
19.
20.<form method="post">
21.
22.ユーザーID:
23.<input required type="text" name="userid" pattern="[0-9]+">
24.<input type="submit" name="send" value="ログイン">
25.
26.</form>
27.
28.
29.</body>
30.</html>