db.collection is not a function? What? - mongodb

Question

I am learning mongodb and following a tutorial with the below code:
My index.js file:
var MongoClient = require('mongodb').MongoClient;
var url = 'mongodb://u****:p****#ds131687.mlab.com:31687/learning_mongo';
var findDocuments = function(db, callback) {
var collection = db.collection('tours');
collection.find().toArray(function(err,docs){
if (err) throw err;
console.log(docs);
callback;
})
}
MongoClient.connect(url, function(err, db){
if (err) throw err;
// console.log("it is working");
// db.close();
findDocuments(db, function(){
db.close();
});
})
Unfortunately, I get the following error in terminal:
dosstx:~/workspace $ node index.js
/home/ubuntu/workspace/node_modules/mongodb/lib/mongo_client.js:810
throw err;
^
TypeError: db.collection is not a function
at findDocuments (/home/ubuntu/workspace/index.js:6:25)
at /home/ubuntu/workspace/index.js:20:5
at args.push (/home/ubuntu/workspace/node_modules/mongodb/lib/utils.js:404:72)
at /home/ubuntu/workspace/node_modules/mongodb/lib/mongo_client.js:255:5
at connectCallback (/home/ubuntu/workspace/node_modules/mongodb/lib/mongo_client.js:933:5)
at /home/ubuntu/workspace/node_modules/mongodb/lib/mongo_client.js:807:13
at _combinedTickCallback (internal/process/next_tick.js:73:7)
at process._tickCallback (internal/process/next_tick.js:104:9)
Does anyone have any advice on how to proceed and/or what is causing the error? The tutorial author does not get this error and I can't see what else is different for me (other than possible different versions of MongoDB vs the author's?)
console.log(db) shows:
MongoClient {
domain: null,
_events: {},
_eventsCount: 0,
_maxListeners: undefined,
s:
{ url: 'mongodb://****:****#ds131687.mlab.com:31687/learning_mongo',
options:
{ user: *****,
password: ****,
socketOptions: {},
read_preference_tags: null,
readPreference: [Object],
dbName: 'learning_mongo',
servers: [Object],
auth: [Object],
server_options: [Object],
db_options: [Object],
rs_options: [Object],
mongos_options: [Object],
socketTimeoutMS: 360000,
connectTimeoutMS: 30000,
promiseLibrary: [Function: Promise] },
promiseLibrary: [Function: Promise],
dbCache: {},
sessions: [] },
topology:
Server {
domain: null,
_events:
{ serverOpening: [Function],
serverDescriptionChanged: [Function],
serverHeartbeatStarted: [Function],
serverHeartbeatSucceeded: [Function],
serverHeartbeatFailed: [Function],
serverClosed: [Function],
topologyOpening: [Function],
topologyClosed: [Function],
topologyDescriptionChanged: [Function],
joined: [Function],
left: [Function],
ping: [Function],
ha: [Function],
authenticated: [Function],
error: [Function],
timeout: [Function],
close: [Function],
parseError: [Function],
open: [Object],
fullsetup: [Object],
all: [Object],
reconnect: [Function] },
_eventsCount: 22,
_maxListeners: undefined,
clientInfo:
{ driver: [Object],
os: [Object],
platform: 'Node.js v6.11.2, LE' },
s:
{ coreTopology: [Object],
sCapabilities: null,
clonedOptions: [Object],
reconnect: true,
emitError: true,
poolSize: 5,
storeOptions: [Object],
store: [Object],
host: 'ds131687.mlab.com',
port: 31687,
options: [Object],
sessionPool: [Object],
promiseLibrary: [Function: Promise] } } }

Answer 1

The connect function has changed on new version of mongodb. This should work
var MongoClient = require('mongodb').MongoClient;
var url = 'mongodb://u****:p****#ds131687.mlab.com:31687/learning_mongo';
var findDocuments = function(db, callback) {
var collection = db.collection('tours');
collection.find().toArray(function(err,docs){
if (err) throw err;
console.log(docs);
callback;
})
}
MongoClient.connect(url, function(err, client){
if (err) throw err;
// console.log("it is working");
// db.close();
findDocuments(client.db('learning_mongo'), function(){
db.close();
});
})
More documentation on this http://mongodb.github.io/node-mongodb-native/3.0/api/

Answer 2

I followed this question and was able to solve the error. Basically, I had to add the following modification to my index.js file:
MongoClient.connect('mongodb://localhost', function (err, client) {
if (err) throw err;
var db = client.db('mytestingdb');
db.collection('customers').findOne({}, function (findErr, result) {
if (findErr) throw findErr;
console.log(result.name);
client.close();
});
});

Answer 3

db.collection() is not a function in the latest version of MongoDB. First uninstall the latest version of MongoDB and then install version number 2.2.33 of MongoDB.
npm uninstall mongodb
npm install mongodb#2.2.33
Version MongoDB >= 3 - That database variable is actually the parent object of the object you are trying to access.