Qfyilyi

Beginning to feel really thick here. Read a lot and I believe I understand promises and async-await decently well. However, I seem to struggle to use the function elsewhere, such that I can obtain the result (e.g. i get pending in another js file with: let dbConnection = dbOperations.openDatabaseConnection();).

Could someone explain to me why do I keep getting pending from the below functions (same function written with promise and asyncawait)? I can console.log the dbConnection result as expected prior to my return within the function. Also, I am particularly keen to understand promises in this sense, as it seems that many npm packages seem to return promises (and with my experience at least the async-await does not sit well with that? -> using async does not wait for resolve in my experience).

// Establish database connection

function openDatabaseConnection() {



    let dbConnection = {};



    return mongodb.connect(dbUri).then(conn => {

        dbConnection.connection = conn;

        return dbConnection;

    })

    .then(() => {

        dbConnection.session = dbConnection.connection.db(dbName);

        //console.log(dbConnection);

        return dbConnection;

    })

    .catch(err => {

        throw err;

    });

};

// Establish database connection

async function openDatabaseConnection() {



    let dbConnection = {};



    try {

        dbConnection.connection = await mongodb.connect(dbUri);

        dbConnection.session = await dbConnection.connection.db(dbName);

    } finally {

        //console.log(dbConnection);

        return dbConnection;

    };

};

Both functions return again a promise.

So in your statement let dbConnection = dbOperations.openDatabaseConnection();
you assign a promise.

Thus you need to do something like:

dbOperations.openDatabaseConnection().then((dbConn) => ..)

or

let dbConnection = await dbOperations.openDatabaseConnection(); 

(note this requires to be wrapped in an async function)

Async/await is just another way to work with Promises, just don't wait for something that isn't a Promise.

async function openDatabaseConnection() {



  let dbConnection = {};



  try {

    dbConnection.connection = await mongodb.connect(dbUri);

    // await here does not make sense, this function does not return a Promise

    // dbConnection.session = await dbConnection.connection.db(dbName);

    dbConnection.session = dbConnection.connection.db(dbName);

  } finally {

    //console.log(dbConnection);

    // return will always execute, keep here only when it should

    // return an empty object if the connection fails

    return dbConnection;

  };

};

More info on async/await