CODEWITHSUNDEEP
node.jsmongodbasynchronousasync-await
JudPeace
JudPeace

Reputation: 13

Await is not waiting

I'm using node js with mongodb. I'm trying to insert an element in the Collection "users" created previously. Afterwards, I delete the Collection and insert two new "users" and print them.

However, the code isn't being executed in the order I was expecting.

I've tried a few different things. For example, removing dropCollection makes it execute in the desired order but I need to use this function for my code. I also tried not using await and obviously, the same result appears.

var MongoClient = require("mongodb").MongoClient;
var url = "mongodb://localhost:27017/mydb";

MongoClient.connect(url, {useNewUrlParser:true}, async function(err, db) {
  if (err) throw err;
  var dbo = db.db("mydb");

  var myobj = { email: "[email protected]", name: "example"};
  await dbo.collection("users").insertOne(myobj, function(err, res) {
    if (err) throw err;
    console.log("1 user inserted");
  });

  await dbo.dropCollection("users", function(err, delOK) {
    if (err) throw err;
    if (delOK) console.log("Collection deleted");
  });

  var myobj = { email: "[email protected]", name: "example"};
  await dbo.collection("users").insertOne(myobj, function(err, res) {
    if (err) throw err;
    console.log("1 user inserted");
  });

  var myobj = { email: "[email protected]", name: "example2"};
  await dbo.collection("users").insertOne(myobj, function(err, res) {
    if (err) throw err;
    console.log("1 user inserted");
  });


  dbo.collection("users").find({}).toArray(function(err, result) {
    if (err) throw err;
    console.log(result);
    db.close();
  });
})

The output I am expecting:

$ npm start
    1 user inserted
    Collection deleted
    1 user inserted
    1 user inserted
    [{ _id: 1234,
      email: '[email protected]',
      name: 'example' },
    { _id: 5678,
      email: '[email protected]',
      name: 'example2' }]

But the output I get is:

$ npm start
    1 user inserted
    1 user inserted
    Collection deleted
    []
    1 user inserted

Upvotes: 1

Views: 858

Answers (2)

Ihor Sakailiuk
Ihor Sakailiuk

Reputation: 6058

You can await only on Promise object. Remove all your callback functions within async context.

const MongoClient = require("mongodb").MongoClient;
const url = "mongodb://localhost:27017/mydb";

MongoClient.connect(url, {useNewUrlParser:true}, async function(err, db) {
  if (err) throw err;
  const dbo = db.db("mydb");

  var myobj = { email: "[email protected]", name: "example"};
  await dbo.collection("users").insertOne(myobj);
  console.log("1 user inserted");

  const delOK = await dbo.dropCollection("users");

  if (delOK) console.log("Collection deleted");

  var myobj = { email: "[email protected]", name: "example"};

  await dbo.collection("users").insertOne(myobj);

  console.log("1 user inserted");

  var myobj = { email: "[email protected]", name: "example2"};
  await dbo.collection("users").insertOne(myobj);

  console.log("1 user inserted");

  const result = await dbo.collection("users").find({}).toArray();

  console.log(result);
  db.close();
})

Upvotes: 2

Tom
Tom

Reputation: 2944

MongoClient uses callbacks rather than Promises so your awaits are currently not doing anything. You can solve this by wrapping the Mongo calls in a Promise and manually resolving them in the callback e.g.

const createUser = async userObj => {
  return new Promise((resolve, reject) => {
    dbo.collection('users').insertOne(userObj, function(err, res) {
      if (err) reject(err);
      resolve('1 user inserted');
    });
  });
};

// ...

await createUser();

Upvotes: 1

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