ivnjavascript,
добавить кодировку utf-8 и слеш
<!DOCTYPE HTML>
<html>
<head>
<title>Untitled</title>
<meta charset="utf-8">
</head>
<body>
<script>
var val = 'Всякая ' , re = new RegExp('^[а-яё\\s]+$', 'i');
alert( val.length >= 1 && re.test(val));
</script>
</body>
</html>