Socket.io why connects twice?

Question

Node.js

Good afternoon.

const io = require('socket.io-client')
const socket = io("http://localhost:1900", {
    transports: ["websocket"]
})

This code connects twice to the server, here is the server console:
hello: eYldOgqbjYxHj152AAAA
hello: eYldOgqbjYxHj152AAAA
And with the same ID

Server code:

io.sockets.on('connection', function (socket) {
    console.log('hello: ' + socket.id)
})

Why can this happen?

Answer 1

Are you doing it in react or native js?
if react then wrap it in useEffect

function main(){
useEffect(()=>{
    const socket = io("http://localhost:1900", {
         transports: ["websocket"]
    })
},[])
}