script.js

          var div = document.createElement('div');
          var container = document.getElementById('container');
          div.className = "chat";
          container.insertBefore(div, div.firstChild);

          var win = Elm.embed(Elm.ChatWindow, div, {
            url: url,
            userId: client.id,
            userName: client.name,
            operatorName: 'Tester'
          });

          win.ports.autoScroll.subscribe(function (event) {
            var chat = div.getElementsByClassName('chat-history')[0];
            chat.scrollTop = chat.scrollHeight
          });
          chatWindows[client.id] = win;