How do you export a variable from app.js into another route in Node js

Question

i'm using socket.io in my node project and wanted to know how to possibly export the io variable

this is what i have done so far but i get this error: Object #<Object> has no method 'on'

in app.js:

        var express = require('express');
var path = require('path');
var favicon = require('serve-favicon');
var logger = require('morgan');
var cookieParser = require('cookie-parser');
var bodyParser = require('body-parser');

var routes = require('./routes/index')(io);
var users = require('./routes/user');

var app = require('express')();
var server = require('http').Server(app);
var io = require('socket.io')(server);
server.listen(4000);

require('./routes/index')(io);

// view engine setup
app.set('views', path.join(__dirname, 'views'));
app.set('view engine', 'jade');

// app.use(favicon(__dirname + '/public/img/favicon.ico'));
app.use(logger('dev'));
app.use(bodyParser.json());
app.use(bodyParser.urlencoded({
  extended: true
}));
app.use(cookieParser());
app.use(express.static(path.join(__dirname, 'public')));

app.use('/', routes);
app.use('/users', users);

/// catch 404 and forward to error handler
app.use(function(req, res, next) {
    var err = new Error('Not Found');
    err.status = 404;
    next(err);
});

/// error handlers

// development error handler
// will print stacktrace
if (app.get('env') === 'development') {
    app.use(function(err, req, res, next) {
        res.status(err.status || 500);
        res.render('error', {
            message: err.message,
            error: err,
            title: 'error'
        });
    });
}

// production error handler
// no stacktraces leaked to user
app.use(function(err, req, res, next) {
    res.status(err.status || 500);
    res.render('error', {
        message: err.message,
        error: {},
        title: 'error'
    });
});
/*
io.on('connection', function (socket) {
  socket.emit('news', { hello: 'world' });
  socket.on('my other event', function (data) {
    console.log(data);
  });
});
*/

module.exports = app;

in index.js

var io = require('../app');

io.on('connection', function (socket) {
  socket.emit('news', { hello: 'world' });
  socket.on('my other event', function (data) {
    console.log(data);
  });
});

the reason i want export the variable is so that i dont have to define io is index.js like i did in app.js which leads to me basically defining both server and app variable !

I just want to do all my socket.io stuff in the index.js route essentially (except from having to redefine the app, server and io variables in index.js ) !

Hope i have explained my self enough

Thank you !

Answer 1

Your dependencies are not set up correctly. You are executing index.js before io is initialized

var routes = require('./routes/index');
/* index.js starts being executed at this point
 * hence, io is undefined inside index.js
 */

Instead, why don't you try

app.js

var app = require('express')();
var server = require('http').Server(app);
var io = require('socket.io')(server);
server.listen(4000);
module.exports = io;

var routes = require('./routes/index');
var users = require('./routes/user');

index.js

 var io = require('../app');

io.on('connection', function (socket) {
    socket.emit('news', { hello: 'world' });
    socket.on('my other event', function (data) {
    console.log(data);
    });
});

Answer 2

I think you need to use the sockets.

io.sockets.on('connection', ... );