MongoDB - Why is Users.findOne undefined?

Question

JavaScript

Hello!
With this code, I want to find an entry in a collection:

var sameLogins = Users.findOne({login: 'a'});
console.log(sameLogins);

But, "undefined" is returned to me, although there is an entry in the collection:

Please tell me what is the problem?
Thank you!

Answer 1

The code above was needed to check user logins for uniqueness.
As it turns out, the meteor has built-in tools for this.
I figured it out thanks to this documentary:
https://docs.meteor.com/api/passwords.html#Account...
This is what the code looks like:

Answer 2

Because Users.findOne is an asynchronous method and the result should be output in a callback or a promise?

var sameLogins = Users.findOne({ login: "a" }, (err, user) => {
  if (err) console.log(err);

  console.log(user);
});

With promises:

var sameLogins = Users.findOne({ login: "a" })
  .then(user => console.log(user))
  .catch(err => console.log(err));