'Sharing' object between NodeJS modules - node.js

Question

I'm new to NodeJS development and I'm doing some tests with the socket.io library. Basically, what I want to do is to stablish a socket.io connection between the clients (Angular 6 web app) and the server and broadcast a message when a new user connects.
Right now, the code is quite simple, and this is what I have:
app.js
var express = require('express');
var http = require('http');
var socketIO = require('socket.io');
// Routes
var twitterRoutes = require('./routes/user');
var app = express();
var server = http.Server(app);
var io = socketIO(server); // <== THIS OBJECT IS WHAT I WANT TO USE FROM THE ROUTES
[ ... ]
io.on('connect', (socket) => {
console.log('New user connected');
socket.on('disconnect', (reason) => {
console.log('User disconnected:', reason);
});
socket.on('error', (err) => {
console.log('Error in connection: ', err);
});
});
I want to use the io object inside the user route, but I don't know how to do it:
routes/user.js
var express = require('express');
var config = require('../config/config');
var router = express.Router();
router.post('/login', (req, res, next) => {
// DO ROUTE LOGIC
// I WANT TO BROADCAST THE NEW LOGGED USER USING io.broadcast.emit, BUT DON'T KNOW HOW
// <=====
});
How could I do it? Thanks in advance,

Answer 1

Not sure if it is the best way but you could share things between request handlers using middleware
// define and use a middleware
app.use(function shareIO(req, res, next) {
req.io = io;
next();
})
Then you could use req.io inside request handlers.
router.post('/login', (req, res, next) => {
// DO ROUTE LOGIC
req.io.emit('event')
});

Answer 2

You could do what you want by injecting your IO var in a function
// app.js
var app = express();
var server = http.Server(app);
var io = socketIO(server);
server.use(require('./router')(io))
...
// router.js
module.exports = function makeRouter(io) {
var router = express.Router();
router.post('/login', (req, res, next) => {
// do something with io
}
return router
}

Answer 3

I don't know if it's the best practice, but I've assigned the io object to a property of the global object, and I can access it from everywhere all across the application. So this is what I did:
app.js
var io = socketIO(server);
global.ioObj = io;
routes/user.js
router.post('/login', (req, res, next) => {
// DO ROUTE LOGIC
if (global.ioObj) {
global.ioObj.sockets.clients().emit('new-message', { type: 'message', text: 'New user has logged in' });
}
});