しばらくしたら削除する一時的なメモ
<!DOCTYPE html> <html> <head> <script src="https://ajax.googleapis.com/ajax/libs/jquery/1.12.4/jquery.min.js"></script> <title>サンプル</title> </head> <body> <script> $(document).on("click", "#btn", function () { const $row = $("input[name='lang']:checked") const $item = $row.closest("tr").find(".number"); alert($item.text().trim()); }); </script> <header> <p>ヘッダー部</p> </header> <div> <table> <tr class="row"> <td> <input type="radio" name="lang" value="ruby">Ruby </td> <td class="number"> 001 </td> </tr> <tr> <td> <input type="radio" name="lang" value="perl">Perl </td> <td class="number"> 002 </td> </tr> </table> <button type="button" id="btn" name="radio-change" value="radio-change">切替</button> </div> <footer>フッター部</footer> </body> </html>