I'm trying to allow users on client-side pages to chat with other users on the same page (a room), but not with users on different pages. Right now my socket is emitting across all pages. I'd like to confine the emissions to one room for each page.

App.js server side code

const io = require('socket.io')(server, { cors: { origin: "*"}});

io.on('connection', (socket) => {
    socket.on('chat message', (msg) => {
        io.emit('chat message', msg);
    });
  });

Client side tag

    <script src="/javascripts/socketIo.js"></script>

SocketIo.js

const socket = io();
const messages = document.getElementById('messages');
const form = document.getElementById('form');
const input = document.getElementById('input');

socket.on('connection', (socket) => {
    socket.join(room);
});

form.addEventListener('submit', function (e) {
    e.preventDefault();
    if (input.value) {
        const alias = socket.id.slice(-5);
        socket.emit('chat message', alias + ": " + input.value);
        input.value = '';
    }
});

socket.on('chat message', function (msg) {
    const item = document.createElement('ul');
    item.textContent = msg;
    messages.appendChild(item);
    window.scrollTo(0, document.body.scrollHeight);
});

The current code sends messages to all users (no rooms). If I update the code below to include prefix "socket.to" like the docs instruct, messages stop sending altogether.

from

socket.emit('chat message', alias + ": " + input.value)

to

socket.to(room).emit('chat message', alias + ": " + input.value)

How do I get socket to send the messages to page-specific rooms?