招待コード入力フォーム

<form class="d10-05-10-form">
          <label>招待コード</label>
          <input type="text" class="d10-05-10-input" placeholder="例)ABCD-1234">
          <button type="submit" class="d10-05-10-btn">参加する</button>
          <p class="d10-05-10-msg"></p>
        </form>

.d10-05-10-form{width:100%;max-width:240px;display:flex;flex-direction:column;gap:8px}
        .d10-05-10-form label{font-size:11.5px;font-weight:700;color:#475569}
        .d10-05-10-input{
          border:1px solid #cbd5e1;border-radius:8px;
          padding:10px 12px;font-size:13px;color:#0f172a;
        }
        .d10-05-10-btn{
          border:none;border-radius:8px;padding:10px 0;
          background:#16a34a;color:#fff;font-size:13px;font-weight:700;cursor:pointer;
        }
        .d10-05-10-msg{margin:2px 0 0;font-size:12px;font-weight:700;color:#16a34a;min-height:16px}

(function(){
        var root = document.querySelector('.d10-05-10');
        var form = root.querySelector('.d10-05-10-form');
        var input = root.querySelector('.d10-05-10-input');
        var msg = root.querySelector('.d10-05-10-msg');
        form.addEventListener('submit', function(e){
          e.preventDefault();
          var code = input.value.trim();
          if(code.length === 0){
            msg.style.color = '#dc2626';
            msg.textContent = '招待コードを入力してください';
            return;
          }
          msg.style.color = '#16a34a';
          msg.textContent = 'コードを確認しました。参加手続きへ進みます';
        });
      })();