how to organize socket handling in node.js and socket.io app

Question

For my REST api I have create a file for each route.

app.get('/api/user', routes.user.index);
app.get('/api/user/login', routes.user.login);

etc, etc.

Now I'm introducing socket.io to the backend and it seems I can only call one function for all socket events.

var socket = require('./socket/stuff.js');

io.sockets.on('connection', function(sock){
    socket.stuff(sock, io);
});

How should I break up the ./socket/stuff.js file (which exports stuff). Into separate files. I would like to eventually replace my REST api with sockets, but I don't want everything to be in one file.

I imagine I would have:

./socket/chat.js
./socket/user.js

etc. etc.

Answer 1

To organize your event handlers in different files, you could use a structure like this:

./main.js

var io = require('socket.io');
var Chat = require('./EventHandlers/Chat');
var User = require('./EventHandlers/User');

var app = {
    allSockets: []
};

io.sockets.on('connection', function (socket) {

    // Create event handlers for this socket
    var eventHandlers = {
        chat: new Chat(app, socket),
        user: new User(app, socket)
    };

    // Bind events to handlers
    for (var category in eventHandlers) {
        var handler = eventHandlers[category].handler;
        for (var event in handler) {
            socket.on(event, handler[event]);
        }
    }

    // Keep track of the socket
    app.allSockets.push(socket);
});

./EventHandlers/Chat.js

var Chat = function (app, socket) {
    this.app = app;
    this.socket = socket;

    // Expose handler methods for events
    this.handler = {
        message: message.bind(this) // use the bind function to access this.app
        ping:    ping.bind(this)    // and this.socket in events
    };
}

// Events

function message(text) {
    // Broadcast message to all sockets
    this.app.allSockets.emit('message', text);
});

function ping() {
    // Reply to sender
    this.socket.emit('message', 'PONG!');
});

module.exports = Chat;

Answer 2

index.js

const httpServer = require("http").createServer();
const io = require("socket.io")(httpServer);

const registerOrderHandlers = require("./orderHandler");
const registerUserHandlers = require("./userHandler");

const onConnection = (socket) => {
  registerOrderHandlers(io, socket);
  registerUserHandlers(io, socket);
}

io.on("connection", onConnection);

orderHandler.js

module.exports = (io, socket) => {  const createOrder = (payload) => {    // ...  }
  const readOrder = (orderId, callback) => {    // ...  }
  socket.on("order:create", createOrder);  socket.on("order:read", readOrder);}

I got it from the documentation. https://socket.io/docs/v4/server-application-structure/