Using Mongodb: TypeError: Cannot read property 'collection' of undefined

Question

Ran in to this problem while doing https://www.freecodecamp.com/challenges/store-data-in-mongodb

error message was

swyx:~/workspace $ learnyoumongo run find.js
/home/ubuntu/.nvm/versions/node/v4.6.1/lib/node_modules/learnyoumongo/node_modules/mongodb/lib/server.js:231
        process.nextTick(function() { throw err; })
                                      ^

TypeError: Cannot read property 'collection' of undefined
    at Exercise.<anonymous> (/home/ubuntu/.nvm/versions/node/v4.6.1/lib/node_modules/learnyoumongo/exercises/find/exercise.js:37:5)
    at next (/home/ubuntu/.nvm/versions/node/v4.6.1/lib/node_modules/learnyoumongo/node_modules/workshopper-exercise/exercise.js:271:17)
    at Exercise.end (/home/ubuntu/.nvm/versions/node/v4.6.1/lib/node_modules/learnyoumongo/node_modules/workshopper-exercise/exercise.js:277:5)
    at Workshopper.end (/home/ubuntu/.nvm/versions/node/v4.6.1/lib/node_modules/learnyoumongo/node_modules/workshopper/workshopper.js:191:12)
    at Workshopper.done (/home/ubuntu/.nvm/versions/node/v4.6.1/lib/node_modules/learnyoumongo/node_modules/workshopper/workshopper.js:323:19)
    at Exercise.<anonymous> (/home/ubuntu/.nvm/versions/node/v4.6.1/lib/node_modules/learnyoumongo/node_modules/workshopper-exercise/exercise.js:160:14)
    at /home/ubuntu/.nvm/versions/node/v4.6.1/lib/node_modules/learnyoumongo/node_modules/workshopper-exercise/exercise.js:147:16
    at /home/ubuntu/.nvm/versions/node/v4.6.1/lib/node_modules/learnyoumongo/exercises/find/exercise.js:20:21
    at /home/ubuntu/.nvm/versions/node/v4.6.1/lib/node_modules/learnyoumongo/node_modules/mongodb/lib/mongo_client.js:238:20
    at /home/ubuntu/.nvm/versions/node/v4.6.1/lib/node_modules/learnyoumongo/node_modules/mongodb/lib/db.js:242:14

there are other similar question on here but none of them were describing this exact problem

for reference this was the (valid) code i was running it on

var mongo = require('mongodb').MongoClient
var age = process.argv[2]

var url = 'mongodb://localhost:27017/learnyoumongo'

mongo.connect(url, function(err, db) {
  if (err) throw err
  var parrots = db.collection('parrots')
  parrots.find({
    age: {
      $gt: +age
    }
  }).toArray(function(err, docs) {
    if (err) throw err
    console.log(docs)
    db.close()
  })
})

i have found my own solution and posted below to help people in future — swyx
– swyx, Commented Nov 26, 2016 at 7:45

swyx · Accepted Answer · 2016-11-26 07:44:44Z

1

solution was my mongodb server experienced an unexpected shutdown overnight and wasn't even running. to start it back up again you have to recover (https://docs.mongodb.com/manual/tutorial/recover-data-following-unexpected-shutdown/) and then restart.

answered Nov 26, 2016 at 7:44

swyx

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2 Comments

Parshuram Kalvikatte Over a year ago

You should add a pm2 service that will keep awake your server

swyx Over a year ago

ok. i dont know what pm2 is but i'll look it up when i have need for it

Pulkit Aggarwal · Accepted Answer · 2018-05-29 17:36:55Z

0

In version 2.x of the MongoDB native NodeJS driver you would get the database object as an argument to the connect callback:

mongo.connect(url, (err, db) => {
  // Database returned
});

But According to the changelog for 3.0 you now get a client object containing the database object instead:

mongo.connect(url, (err, client) => {
  // Client returned
  var db = client.db('mytestingdb');
});

The close() method has also been moved to the client so that you have to write client.close(); instead of db.close()

answered May 29, 2018 at 17:36

Pulkit Aggarwal

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