Mongoose "disconnect is not a function"

Question

I'm using this tutorial to make a node/mongo application. When I run addContact, it seems like the contact saves to the DB but, I get an error saying that the disconnect function is not a function. Can anyone tell me why this is happening and, how to fix it? I'm assume that there's some issue with the scope of the constant, db?

code:

const mongoose = require('mongoose'); 
const assert = require('assert'); 
mongoose.Promise = global.Promise; 


const db = mongoose.connect('mongodb://localhost:27017/contact-manager');


function toLower(v) {
  return v.toLowerCase();
}

const contactSchema = mongoose.Schema({
  firstname: { type: String, set: toLower },
  lastname: { type: String, set: toLower },
  phone: { type: String, set: toLower },
  email: { type: String, set: toLower }
});


const Contact = mongoose.model('Contact', contactSchema);

const addContact = (contact) => {
  Contact.create(contact, (err) => {
    assert.equal(null, err);
    console.info('New contact added');
    db.disconnect();
  });
};

const getContact = (name) => {
  const search = new RegExp(name, 'i');
  Contact.find({$or: [{firstname: search }, {lastname: search }]})
  .exec((err, contact) => {
    assert.equal(null, err);
    console.info(contact);
    console.info(`${contact.length} matches`);
    db.disconnect();
  });
};

module.exports = {  addContact, getContact };

code part2:

const program = require('commander');

const {addContact, getContact} = require('./logic');

program
  .version('0.0.1')
  .description('Contact management system');

program
  .command('addContact <firstame> <lastname> <phone> <email>')
  .alias('a')
  .description('Add a contact')
  .action((firstname, lastname, phone, email) => {
    addContact({firstname, lastname, phone, email});
  });

program
  .command('getContact <name>')
  .alias('r')
  .description('Get contact')
  .action(name => getContact(name));

program.parse(process.argv);

error:

New contact added
/Users/user/contact-manager/node_modules/mongodb/lib/utils.js:132
      throw err;
      ^

TypeError: db.disconnect is not a function
    at Contact.create (/Users/user/contact-manager/logic.js:33:8)
    at Function.<anonymous> (/Users/user/contact-manager/node_modules/mongoose/lib/model.js:3913:16)
    at parallel (/Users/user/contact-manager/node_modules/mongoose/lib/model.js:2077:12)
    at /Users/user/contact-manager/node_modules/async/internal/parallel.js:35:9
    at /Users/user/contact-manager/node_modules/async/internal/once.js:12:16
    at iteratorCallback (/Users/user/contact-manager/node_modules/async/eachOf.js:52:13)
    at /Users/user/contact-manager/node_modules/async/internal/onlyOnce.js:12:16
    at /Users/user/contact-manager/node_modules/async/internal/parallel.js:32:13
    at apply (/Users/user/contact-manager/node_modules/lodash/_apply.js:15:25)
    at /Users/user/contact-manager/node_modules/lodash/_overRest.js:32:12
    at callbackWrapper (/Users/user/contact-manager/node_modules/mongoose/lib/model.js:2046:11)
    at /Users/user/contact-manager/node_modules/mongoose/lib/model.js:3913:16
    at model.$__save.error (/Users/user/contact-manager/node_modules/mongoose/lib/model.js:342:7)
    at /Users/user/contact-manager/node_modules/kareem/index.js:297:21
    at next (/Users/user/contact-manager/node_modules/kareem/index.js:209:27)
    at Kareem.execPost (/Users/user/contact-manager/node_modules/kareem/index.js:217:3)

Answer 1

mongoose.connect does not return a value, as far as I can tell from looking at the code given in the getting started guide. If you want to close the database connection, you need to call the close method on mongoose.connection which is written to when you open a connection with mongoose.connect. The simplest way to do this is to move your mongoose.connect to its own line:

mongoose.connect('mongodb://localhost:27017/contact-manager');
const db = mongoose.connection;

Then just replace your calls to db.disconnect() with calls to db.close().