cannot read property 'emit' of undefined socketio

Question

I'm building a project using socket.io. while running getting the error "TypeError: Cannot read property 'emit' of undefined".

server code is given below:

server.js

const express = require('express')
const app = express()
const server = require('http').Server(app)
const io = require('socket.io')(server)
const { v4: uuidV4 } = require('uuid')

app.set('view engine', 'ejs')
app.use(express.static('public'))

app.get('/', (req, res) => {
  res.redirect(`/${uuidV4()}`)
})

app.get('/:room', (req, res) => {
  res.render('room', { roomId: req.params.room })
})

io.on('connection', socket => {
  socket.on('join-room', (roomId, userId) => {
    socket.join(roomId)
    socket.to(roomId).broadcast.emit('user-connected', userId)

    socket.on('disconnect', () => {
      socket.to(roomId).broadcast.emit('user-disconnected', userId)
    })
  })
})

server.listen(3000)

Can anyone help to rectify the error?

Answer 1

It seems that your socket function is written in the wrong order

Try this:

socket.broadcast.to(roomId).emit('user-connected', userId)

and this:

  socket.broadcast.to(roomId).emit('user-disconnected', userId)