nodejs return array of objects from mongodb

Question

I want to return an array of objects that contains collection name and its documents count for each object, e.g. [ { col:col1, count:1 } , { col:col2, count:2} ]

Currently I only return an array of document count for each collection, by resolving the query as a promise.

My main issue is returning an object from the .map function because it must return promises instead.

db.listCollections()
  .toArray()
  .then(collections => {
    let promises = collections.map(col => {

      // Cannot return {col,count} here :/
      return db.collection(col["name"]).countDocuments();
    });
    return Promise.all(promises);
  })
  .then(res => console.log(res));

Patrick Roberts · Accepted Answer · 2018-07-18 15:22:58Z

1

Alternatively, passing an async function to collections.map(), you could return { col, count }:

db.listCollections()
  .toArray()
  .then(collections => {
    const promises = collections.map(async col => {
      return {
        col: col.name,
        count: await db.collection(col.name).countDocuments()
      };
    });
    return Promise.all(promises);
  })
  .then(res => { console.log(res); });

answered Jul 18, 2018 at 15:22

Patrick Roberts

52.4k10 gold badges120 silver badges166 bronze badges

Sign up to request clarification or add additional context in comments.

Comments

the_dude · Accepted Answer · 2018-07-18 15:17:35Z

0

Fixed it with

return Promise.all([
    db.collection(col["name"]).countDocuments(),
    Promise.resolve(col["name"])
]);

answered Jul 18, 2018 at 15:17

the_dude

399 bronze badges

1 Comment

Patrick Roberts Over a year ago

The Promise.resolve() around col["name"] is not necessary, and you also don't need a computed property to do that, so the simplified answer would be return Promise.all([db.collection(col.name).countDocuments(), col.name])

Collectives™ on Stack Overflow

nodejs return array of objects from mongodb

2 Answers 2

Comments

1 Comment

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

Comments

1 Comment

Your Answer

Sign up or log in

Post as a guest

Related