Untitled

<!DOCTYPE HTML>
<html>
<head>
    <meta charset="utf-8">
    <title>length</title>
</head>
<body>
<p id="elem" class="www ggg zzz"></p>
<script>
    let p = document.querySelector('#elem');
    let button = document.querySelector('.btn');
    for (let i = 1; i <= 10; i++) {
       {
            alert( p.className.trim().split(/\s+/) );
        }
    }
</script>
</body>
</html>