Get username object without requesting it after authentication? (Node & express.js) - node.js

Question

I'm making a Node backend using express (also using bcrypt for password hashing and jsonwebtoken for authorization). My requests are in separate files and they all use module.exports. I have this login request that is in a file called login.js:
router.post("/account/login", async (req, res) => {
// User object
const user = {
username: req.body.username,
password: req.body.password
};
// Get user name only
const username = {
username: req.body.username
};
// Create a new JWT token
const token = jwt.sign(username, secret);
// Get username as a string
const usernameString = JSON.stringify(user.username);
// Get hashed password from the collection
const hashedPassword = await logincollection.findOne({ username: req.body.username });
// Search for matching login credentials
await logincollection.findOne(username, (err, result) => {
// If username was not found, return code 400
if (result == null) {
res.status(400).send();
}
// Proceed if username was found
else {
// If no token was given, return code 401
if (!token) {
res.status(401).send();
}
// Verify the given JWT token
jwt.verify(token, secret, (err, decoded) => {
// If verification failed, return code 500
if (err) {
res.status(500).send();
}
})
// Use bcrypt to compare the passwords and authenticate login
bcrypt.compare(req.body.password, hashedPassword.password).then(match => {
// If the credentials match
if (match) {
// Insert the token into a cookie
res.cookie("token", token, { httpOnly: true });
// Return code 200
res.status(200).send({ auth: true, token: token });
// Log to console when user logs in
console.log("User " + usernameString + " logged in");
}
// If the credentials do not match
else {
// Return code 404
res.status(400).send();
}
// If comparing fails
}).catch(error => {
// Return code 500
res.status(500).send();
})
}
})
})
Every user has their own collection in a MongoDB database that is created, when the account is created. These collections are named after the username, since usernames are unique here. In this load.js file I have a request that loads all the objects in the collection:
router.post("/note/load", async (req, res) => {
// User object
const username = {
username: req.body.username
};
// Get usercollection depending on username
const usercollection = userdb.collection(JSON.stringify(username));
// Load the notes
const loadNote = await usercollection.find().toArray();
// Return code 200 and sendObject
res.status(200).send(loadNote);
})
Obviously, the code above will result in an error, because the username is not given in the request. Is there a way to pass the username to any request, when needed? Or can I use JWT for this, and if so, how? I have tried storing usernames in a variable, but that doesn't work, since the variable gets overwritten, when two users are logged in at the same time.
PS. The title is poor, because I don't know how to put this shortly. If you have any suggestions or corrections regarding the question or the title, please comment below.