$ npm install firebase-fcm-plugin

var FCM = require('firebase-fcm-plugin');

const fcmConfig = {
    projectId : '',
    client_email : '',
    private_key : ''
};
const fcm = new FCM(fcmConfig);

var message = {
    token: 'registration_token_or_topics_name_with_prefix', // required fill with device token or `/topics/${topicName}`
    notification: {
        title: 'Title of your push notification',
        body: 'Body of your push notification'
    }
};

//callback style
fcm.send(message, function(err, response){
  if (err) {
      console.log("Something has gone wrong!");
  } else {
      console.log("Successfully sent with response: ", response);
  }
});

//promise style
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);
})