title: Sending Firebase Notification with nodejs
body: <p>I have an android app on which I want to send notification via my web app.</p>
  
  <p>How do I send Firebase Cloud Messaging notification with nodejs? I have found a lot of examples and posts on this subject, but in all of them you are supposed to just paste device Token and send notification to that device. If I wanted to use it that way, I would be able to simply implement this from official documentation.</p>
  
  <p>The thing is, I need to receive user id from database so I know which user I want to send notification. After I have user id I can then retrieve device Token from the same database. I get both user id and device token on client side. And documentation refers to server side. </p>
  
  <p>This all happen after button click. So, I don't understand how to send notification on server side, meaning, I don't have there all those informations I need - user id, device token and message info that contain some other database info. Do I pass those arguments from client side to server side somehow, or is there a way of using modules like "require()" on client side?
  What is the best approach here?</p>