MongoDB の検証

const MongoClient = mongodb.MongoClient;
// Connection URL
const url = "XXXXXX";
query = JSON.parse(query);

const client = new MongoClient(url, { useNewUrlParser: true });

const connect = () => {
  return new Promise((resolve, reject) => {
    client.connect(function(err) {
      if (err) {
        return reject(err);
      }
      console.log("Connected successfully to server");
      const db = client.db(dbName);
      resolve(db);
    });
  });
};

const findOne = (db, collName) => {
  return new Promise((resolve, reject) => {
    const coll = db.collection(collName);
    coll.findOne(query, (err, result) => {
      if (err) {
        return reject(err);
      }
      console.log("Got collection result");
      resolve(result);
    });
  });
};

return connect()
  .then(db => findOne(db, collName, query))
  .then(result => {
    if (!result) {
      return Promise.reject(new Error("Failed to find object"));
    }
  })
  .finally(() => client.close());