is there a way to automatically scroll to the last item after appending from a javascript event to an unordered list?

Question

I am developing a simple chat app using javascript and socket.io with node.js

Everything works well, except when chat messages are appended when a chat message is received, the list of chat messages grows but stays at the top instead of scrolling to the bottom to show the last message that arrived.

I have tried all suggestions but the list keeps appending the messages but stays on the top showing the oldest message first and the new ones are not shown unless I manually scroll the list with the mouse

Your help will be greatly appreciated.

Thank you

here is the code:

<!doctype html>
<html>
  <head>
    <title>Socket.IO chat</title>
    <style>
      * { margin: 0; padding: 0; box-sizing: border-box; }
      body { font: 13px Helvetica, Arial; }
      form { background: #000; padding: 3px; position: fixed; bottom: 0; width: 100%; }
      form input { border: 0; padding: 10px; width: 90%; margin-right: .5%; }
      form button { width: 9%; background: rgb(130, 224, 255); border: none; padding: 10px; }
      #messages { list-style-type: none; margin: 0; padding: 0;}
      #messages li { padding: 5px 10px; }
      #messages li:nth-child(odd) { background: #eee; }
    </style>
  </head>
  <body>
    <ul id="messages"></ul>
    <form action="">
      <input id="m" autocomplete="off" /><button>Send</button>
    </form>
<script src="/socket.io/socket.io.js"></script>
<script src="https://code.jquery.com/jquery-1.11.1.js"></script>
<script>
  $(function () {
    var socket = io();
    $('form').submit(function(e){
      e.preventDefault(); // prevents page reloading
      socket.emit('chat message', $('#m').val());
      $('#m').val('');
      return false;
    });
    socket.on('chat message', function(msg){
      $('#messages').append($('<li>').text(msg));
    });
  });
</script>
  </body>
</html>

and here is the server code run with node.js


var app = require('express')();
var http = require('http').createServer(app);
var io = require('socket.io')(http);

app.get('/', function(req, res){
    console.log('about to send:'+__dirname + '/index.html');
  res.sendFile(__dirname + '/index.html');
});
io.on('connection', function(socket){
  socket.on('chat message', function(msg){
    io.emit('chat message', msg);
  });
});

http.listen(3000, function(){
  console.log('listening on *:3000');
});

Does this answer your question? [Scroll to bottom of div?](https://stackoverflow.com/questions/270612/scroll-to-bottom-of-div) — Anurag Srivastava, Apr 02 '20 at 17:26
are you saying you need to browser window to scroll down to the bottom of a certain element? — Nibb, Apr 02 '20 at 17:44
yes, the
element stays on the top instead of scrolling up to show the last chat message added — Rodolfo, Apr 02 '20 at 18:16

score 0 · Answer 1 · answered Apr 02 '20 at 17:30

use scrollTop to go after add new one

  <script>
      $(function () {
        var socket = io();
        $('form').submit(function(e){
          e.preventDefault(); // prevents page reloading
          socket.emit('chat message', $('#m').val());
          $('#m').val('');
          return false;
        });
        socket.on('chat message', function(msg){
          $('#messages').append($('<li>').text(msg));
         var ul= document.getElementById("messages");
         ul.scrollTop = ul.scrollHeight;
        });
      });
    </script>

thank you for your quick answer. I tried it but the list does not scroll to show the last message added , do I need to add some kind of auto refresh instruction? — Rodolfo, Apr 02 '20 at 18:15

score 0 · Accepted Answer · answered Apr 02 '20 at 20:21

I have a chat app that uses this jQuery code to smoothly scroll to the bottom of the document. The animation takes 800 milliseconds.

    // scroll to bottom of display
    $('html, body').animate({scrollTop:$(document).height()}, 800);

Docs for jQuery.animate() and Element.scrollTop.

is there a way to automatically scroll to the last item after appending from a javascript event to an unordered list?

2 Answers2