<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"> <html> <head> <meta http-equiv="Content-Type" content="text/html; charset=utf-8"> <title>ラジオボタン (オプションボタン)</title> <link href="/gudon/css/default.css" rel="stylesheet" type="text/css" /> </head> <body> <h1>ラジオボタン (オプションボタン)</h1> <hr /> <form name="form1" action="test1.php" onsubmit="return form1_onsubmit();"> <input type="radio" name="radioGroup1" value="radioValue1">ラジオボタン1 <input type="radio" name="radioGroup1" value="radioValue2">ラジオボタン2 <input type="radio" name="radioGroup1" value="radioValue3">ラジオボタン3 <input type="submit" value="submit"> </form> <script type="text/javascript"> function form1_onsubmit() { var radioGroup1 = document.form1.radioGroup1; for(var i = 0; i < radioGroup1.length; i++) { if(radioGroup1[i].checked) { return true; } } alert("どれか一つを、必ず選択してください。"); return false; } </script> </body> </html>