Node.js Async/Await module export

Question

I\'m kinda new to module creation and was wondering about module.exports and waiting for async functions (like a mongo connect function for example) to complete and exportin

Answer 1

the solution provided above by @Jonas Wilms is working but requires to call requires in an async function each time we want to reuse the connection. an alternative way is to use a callback function to return the mongoDB client object.

mongo.js:

const MongoClient = require('mongodb').MongoClient;

const uri = "mongodb+srv://<user>:<pwd>@<host and port>?retryWrites=true";

const mongoClient = async function(cb) {
    const client = await MongoClient.connect(uri, {
             useNewUrlParser: true
         });
         cb(client);
};

module.exports = {mongoClient}

then we can use mongoClient method in a diffrent file(express route or any other js file).

app.js:

var client;
const mongo = require('path to mongo.js');
mongo.mongoClient((connection) => {
  client = connection;
});
//declare express app and listen....

//simple post reuest to store a student..
app.post('/', async (req, res, next) => {
  const newStudent = {
    name: req.body.name,
    description: req.body.description,
    studentId: req.body.studetId,
    image: req.body.image
  };
  try
  {

    await client.db('university').collection('students').insertOne({newStudent});
  }
  catch(err)
  {
    console.log(err);
    return res.status(500).json({ error: err});
  }

  return res.status(201).json({ message: 'Student added'});
};

Answer 2

You have to export synchronously, so its impossible to export client and db directly. However you could export a Promise that resolves to client and db:

module.exports = (async function() {
 const client = await MongoClient.connect(url, {
   useNewUrlParser: true
 });

  const db = client.db(mongo_db);
  return { client, db };
})();

So then you can import it as:

const {client, db} = await require("yourmodule");

(that has to be in an async function itself)

PS: console.error(err) is not a proper error handler, if you cant handle the error just crash