Vedi se cosi possa andare bene:
codice:
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>Documento senza titolo</title>
<script type="text/javascript">
function FormattaOra(ora){
var maxora = "24"
var maxminuti = 59
if(ora.value.length<4){
alert("Errore orario troppo corto");}
else if(ora.value.length>4 && ora.value.indexOf(":")==-1){
alert("Errore inserisci massimo 5 caratteri compresi i 2 punti :");
ora.value=ora.value.replace(ora.value.substr(2),':');}
else if(!ora.value.match(/^[0-9 :]/g)){
alert("Inseire l\'ora nel formato 00:00");ora.value=''}
else if(ora.value.substr(0,2)>maxora){
alert("Ora errata");
ora.value='';
}else if((ora.value.substr(3,5)>maxminuti) || (ora.value.substr(2,3)>maxminuti)){
alert("Minuti errati");
ora.value=ora.value.substr(0,ora.value.length-2);}
else if(ora.value.indexOf(":")==-1){
ora.value=ora.value.replace(ora.value.substr(2),':')+ora.value.substr(2,4)
}
}
</script>
</head>
<body>
<form id="form1" name="form1" method="post" action="">
<input type="text" name="ora" id="ora" onblur="FormattaOra(this)" />
</form>
</body>
</html>
Consiglio verifica il campo anche al submit del forum