Returning an array from mongodb connect and find

Question

I have the following code that I use to connect to my MongoDB instance and return some recored. I need to iterate over the cursor results to create a suitable data structure for my application. However, I struggling to work out how to return the contents of the table array to the calling function. It works if I predefine a table variable but that is not what I need to achieve.

How can I get the findUsage function to return the table array to the callingMongoClient.connect code?

const MongoClient = require('mongodb').MongoClient
const assert = require('assert')
const url = 'mongodb://localhost:27017/test'

const table = []
const findUsage = function (db, callback) {
    const cursor = db.collection('usage')
        .find({ },
            {'customer': 1})
    cursor.each(function (err, doc) {
        assert.equal(err, null)
        if (doc != null) {
            table.push(
                [doc.customer]
            )
        } else {
            callback(table)
        }
    })
}

MongoClient.connect(url, function (err, db) {
    assert.equal(null, err)
    findUsage(db, function () {
        //      console.log("Session: %j", table);
        console.log(table)
        db.close()
    })
})

Orelsanpls · Accepted Answer · 2017-09-28 12:03:58Z

2

Use the method toArray to deal with the find cursor. Then use the callback, either if there is data or not.

        const findUsage = function (db, callback) {
          const cursor = db.collection('usage')
            .find({}, {
              'customer': 1,
            });

          cursor.toArray(function (err, docs) {
            assert.equal(err, null);

            if (docs) {
              return callback(docs.map(x => x.customer));
            }

            return callback([]);
          });
        }

        MongoClient.connect(url, function (err, db) {
          assert.equal(null, err);

          findUsage(db, function (docs) {
            // ...

            db.close();
          });
        });

answered Sep 28, 2017 at 12:03

Orelsanpls

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1 Comment

user1513388 Over a year ago

Arh thanks. How do I get to the data in the MongoClient.connect call. e.g. console.log(??) ?

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