Untitled

<html>
<head>
<title>
title
</title>
</head>
<body>
<script>
var letters = 'So, today we have REALLY good day';
var ltters = 'So, today we have REALLY good day';
    for(var i = 0; i<letters.length; i++){
        if(letters[i] === letters[i].toLowerCase()){
            ltters = letters[i].toUpperCase();
        }else {
            ltters = letters[i].toLowerCase();
        }

document.write(ltters);
    }


</script>
</body>
</html>