First, you will need to install Push.js module.

$ npm install push.js --save

Or import it to your front-end app through CDN

<script src="./push.min.js"></script> <!-- CDN link -->

After you are done with that, you should be good to go. This is how it should look like if u wanna make simple notification:

Push.create('Hello World!')

I will assume that you know how to setup Socket.io with your app. Here is some code example of my backend app with express:

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

server.listen(80);

app.get('/', function (req, res) {
  res.sendfile(__dirname + '/index.html');
});

io.on('connection', function (socket) {
  
  socket.emit('pushNotification', { success: true, msg: 'hello' });

});

After your server is all set up, you should be able to move on to front-end stuff. Now all we have to do is import Socket.io CDN and add this code to my index.html file:

<script src="../socket.io.js"></script> <!-- CDN link -->
<script>
  var socket = io.connect('http://localhost');
  socket.on('pushNotification', function (data) {
    console.log(data);
    Push.create("Hello world!", {
        body: data.msg, //this should print "hello"
        icon: '/icon.png',
        timeout: 4000,
        onClick: function () {
            window.focus();
            this.close();
        }
    });
  });
</script>

There you go, now you should be able to display your notification, this also works on any Android device, and if u wanna use Firebase cloud messaging, you can use it with this module, Here is link for that example written by Nick (creator of Push.js)

Keep in mind that this will not work on Apple devices (I didnt test them all), but if you want to make push notifications check OneSignal plugin.