node.js - db.collection is not a function when using MongoClient v3.0

Question

I have been trying W3schools tutorial on nodeJS with MongoDB.

When I try to implement this example in a nodeJS environment and invoke the function with an AJAX call, I got the error below:

TypeError: db.collection is not a function
    at c:UsersuserDesktopWeb ProjectWebService.JS:79:14
    at args.push (c:Usersuser
ode_modulesmongodblibutils.js:431:72)
    at c:Usersuser
ode_modulesmongodblibmongo_client.js:254:5
    at connectCallback (c:Usersuser
ode_modulesmongodblibmongo_client.js:933:5)
    at c:Usersuser
ode_modulesmongodblibmongo_client.js:794:11
    at _combinedTickCallback (internal/process/next_tick.js:73:7)
    at process._tickCallback (internal/process/next_tick.js:104:9)

Please find below my implemented code:

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

MongoClient.connect(url, function(err, db) {
  if (err) throw err;
  db.collection("customers").findOne({}, function(err, result) {
    if (err) throw err;
    console.log(result.name);
    db.close();
  });
});

Note that the error occurs whenever the execution hits:

db.collection("customers").findOne({}, function(err, result) {}

Also, note (in case it matters) that I have installed the latest MongoDB package for node JS (npm install mongodb), and the MongoDB version is MongoDB Enterprise 3.4.4, with MongoDB Node.js driver v3.0.0-rc0.

Answer 1

For people on version 3.0 of the MongoDB native NodeJS driver:

(This is applicable to people with "mongodb": "^3.0.0-rc0", or a later version in package.json, that want to keep using the latest version.)

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

MongoClient.connect('mongodb://localhost:27017/mytestingdb', (err, db) => {
  // Database returned
});

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

MongoClient.connect('mongodb://localhost:27017', (err, client) => {
  // Client returned
  var db = client.db('mytestingdb');
});

The close() method has also been moved to the client. The code in the question can therefore be translated to:

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();
  });
});