Generate custom socket id for socket.io - node.js

Question

According to socket.io documentation for generating custom id this should work:
const express = require('express');
const app = express();
const server = require('http').createServer(app);
const io = require('socket.io')(server);
require('dotenv').config();
io.engine.generateId = (req) => {
// generate a new custom id here
var randomCode = '';
for (let r = 0; r < 6; r++) {
randomCode += Math.floor(Math.random() * 10)+'';
}
return randomCode
}
io.on('connection', (socket) => {
console.log("a user connected :D", socket.id);
socket.on('storeClientInfo', (data) => {
console.log(socket.id)
});
socket.on("private message", (anotherSocketId, msg) => {
console.log(anotherSocketId, msg)
socket.to(anotherSocketId).emit("private message", socket.id, msg);
});
});
server.listen(4000);
app.listen(process.env.PORT, () => console.log('Server is running'));
but it doesn't work for me the console outputs:
a user connected :D wJ8d-SC2su9YYCdWAAAC
it should be 6 random numbers, the random number is just for testing I want to assign the id to the user id in the database later.

Answer 1

use can assign custom params to socket
var users = []
io.use((socket, next) => {
socket.customId = 123456789;
users[socket.customId] = socket;
next()
});
and you can use custom params in
io.on("connection", (socket) => {
socket.on("sendPrivateMessage", params => {
users[params.toUserId].emit("message", "you have a private message")
})
});