How to do MongoDB atomic “findOrCreate”: findOne, insert if nonexistent, but do not update with JavaScript?

To do MongoDB atomic "findOrCreate": findOne, insert if nonexistent, but do not update with JavaScript, we use the findAndModify method.

For instance, we write

db.collection.findAndModify({
  query: { _id: "id" },
  update: {
    $setOnInsert: { foo: "bar" },
  },
  new: true,
  upsert: true,
});

to call findAndModify with an object with the query to look for the item with the ID 'id'.

We set update to the field on update.

upsert is set to true to insert a new entry if the item doesn’t exist.