Scrollbar focus on the bottom of the HTML div

nice and simple just put this code somewhere in your script, preferably the top

     <script>
     var objDiv = document.getElementById("chatbox");
     if ( window.history.replaceState ) {
     objDiv.scrollTop = objDiv.scrollHeight;

      window.history.replaceState( null, null, 
      window.location.href );
      }
      </script>

You can use Element.scrollIntoView()

Example:

document.getElementById('your_div').scrollIntoView()

Demo:

document.getElementById("my_div").scrollIntoView();

.page-body {
  overflow: auto;
  max-height: 200px;
}

<div class="page-body">
  <p>lorem ipsum</p>
  <p>lorem ipsum</p>
  <p>lorem ipsum</p>
  <p>lorem ipsum</p>
  <p>lorem ipsum</p>
  <p>lorem ipsum</p>
  <p>lorem ipsum</p>
  <p>lorem ipsum</p>
  <p>lorem ipsum</p>
  <p>lorem ipsum</p>
  <p>lorem ipsum</p>
  <p id="my_div">lorem ipsum</p>
</div>