// If you don't know when data comes, you can set an interval:
window.setInterval(function() {
  var elem = document.getElementById('yourDivWithScrollbar');
  elem.scrollTop = elem.scrollHeight;
}, 5000);

// If you do know when data comes, you can do it like the following:
var elem = document.getElementById('yourDivWithScrollbar');
elem.scrollTop = elem.scrollHeight;