<body>
<table id=myTable>
<tr class=alert-danger><td>1</td><td>Class</td><tr>
<tr><td>2</td><td>No class</td><tr>
<tr><td>3</td><td>No class</td><tr>
<tr class=alert-danger><td>4</td><td>Class</td><tr>
<tr><td>5</td><td>No class</td><tr>
<tr class=alert-danger><td>6</td><td>Class</td><tr>
</table>
<script>
function dangerUp () {
const tab = document.getElementById('myTable');
const trnocl = tab.querySelector('tr:not(.alert-danger)'); // первая строка без класса
if (!trnocl) return;
const trscl = tab.querySelectorAll('tr.alert-danger'); // все строки с классом
trnocl.before(...trscl);
}
dangerUp();
</script>
</body>