MongoDB collection/Express.js for "friend request" functionality

I have an idea for how to store the relationships. Each user has a friends Array filled with IDs. However, how should I initiate a friend request in my Express.js app in MongoDB?

I'm thinking about creating a "notifications" collection with:

_id, userId, type, friendId, read

So when the requested friend logs in, they can see all of their own notifications to deal with...

Or is that ridiculous?

Sounds reasonable enough. But my approach will be a little different. I would store the notifications in the user db itself. Something like

username
dob
...
notifications[[type: 'friend', read: 0, request_from: '22sd300sdf45003425asz'], ...]
...

This way, you don't have to make a db call on every page load. As soon as you initialize a session (I use passport), it will be there, ready already for templates. After a valid action from the user, I can delete it or whatever.

But again, its dependent on the need. Do what suits you best!