mongoose findOneOrCreate solution

pageSchema.statics.findOneOrCreate = function findOneOrCreate(condition, doc, callback) {
  const self = this;
  self.findOne(condition, (err, result) => {
    return result 
      ? callback(err, result)
      : self.create(doc, (err, result) => {
        return callback(err, result);
      });
  });
}

Now when you have an instance of Page you can call findOneOrCreate:

Page.findOneOrCreate({id: 'somePageId'}, (err, page) => {
  console.log(page);
});