Example Using of fcm-push-notif modules https://github.com/eFishery/fcm-push-notif

fcm-push-notif.js

var FCM = require('fcm-push-notif');

var serverKey = 'firebase_server_key';
var fcm = new FCM(serverKey);

var message = {
    to: '/topics/news', // required could be topic url or device registration token
    collapse_key: 'your_collapse_key', 
    data: {
        message: 'This is data message'
    },
    notification: {
        title: 'Test',
        body: 'test message'
    }
};

fcm.send(message)
    .then(function(response){
        console.log("Successfully sent with response: ", response);
    })
    .catch(function(err){
        console.log("Something has gone wrong!");
        console.error(err);
    })