Get Firestore generated doc ID after set

Question

Is there a way to get the generated doc Id after you've saved a document to firestore?

var collection = db.collection("Users").doc();
collection.set({
                  xxx:"stuff",
                  yyy:"stuff"
               })
                .then(function (?Something?) 
                  {
                    var theIdIWant = ?Something?;
                  }
               )

Edit: Or just

var myID = collection.id

Answer 1

The return value from doc() is a DocumentReference which has the unique id in its id field.

var doc = db.collection("Users").doc();
doc.set({
    xxx:"stuff",
    yyy:"stuff"
})
.then(() => { 
    var theIdIWant = doc.id
})