use socket.io code example

Example 1: socket io script

<script src="/socket.io/socket.io.js"></script>
<script>
  const socket = io();
</script>

Example 2: socket io connect to namespace

var io  = require('socket.io')(http, { path: '/myapp/socket.io'});

io
.of('/my-namespace')
.on('connection', function(socket){
    console.log('a user connected with id %s', socket.id);

    socket.on('my-message', function (data) {
        io.of('my-namespace').emit('my-message', data);
        // or socket.emit(...)
        console.log('broadcasting my-message', data);
    });
});

Example 3: js socket.emit

const socket = io('ws://localhost:3000');
socket.on('connect', () => {  
  // either with send()  
  socket.send('Hello!');
  // or with emit() and custom event names  
  socket.emit('salutations', 'Hello!', { 'mr': 'john' }, Uint8Array.from([1, 2, 3, 4]));});
// handle the event sent with socket.send()
socket.on('message', data => {
  console.log(data);
});
// handle the event sent with socket.emit()
socket.on('greetings', (elem1, elem2, elem3) => {
  console.log(elem1, elem2, elem3);
});

Example 4: socket.io documentation

const socket = new WebSocket('ws://localhost:3000');socket.onopen(() => {  socket.send('Hello!');});socket.onmessage(data => {  console.log(data);});