How to dynamically delete data rows in a table through JS (keep the head)

How to use JS Delete dynamically table Data rows in （ Retain head）

    var Oldtab = document.getElementById(tableID);
    var rowNum = Oldtab.rows.length-1;
    for(var i=0; i<rowNum; i++)
    {
    
      Oldtab.deleteRow(Oldtab.rows.length-1);	//Delete the last row
    }