codice:
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<script language="javascript" type="text/javascript">
function prova(campo)
{
document.mioform.nome2.value = campo;
}
</script>
<title>Documento senza titolo</title>
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
</head>
<body>
<form name="mioform">
<input name="nome" type="text">
<input type="button" value="Clic" onClick="prova('nome')">
<input name="nome2" type="text">
</form>
</body>
</html>
ciao