learnyoumongo Coding Challenges Solutions

solution.js

//Solution 9
const url = 'mongodb://localhost:27017/learnyoumongo';
const mongo = require('mongodb').MongoClient;
mongo.connect(url, function(err, dbobj){
  if(err) throw err;
  const lym = dbobj.db('learnyoumongo');
  var prices = lym.collection('prices');
  prices.aggregate([{
    $match: {
      size: process.argv[2]
    }
  },{
    $group: {
      _id: 'average',
      average:{
        $avg: '$price'
      }
    }
  }]).toArray(function(err, res){
    if(err) throw err;
    console.log(Number(+res[0].average).toFixed(2));
  });
});


//Solution 8
const url = 'mongodb://localhost:27017/learnyoumongo';
const mongo = require('mongodb').MongoClient;
mongo.connect(url, function(err, dbobj){
  if(err) throw err;
  const lym = dbobj.db('learnyoumongo');
  var parrots = lym.collection('parrots');
  parrots.count({
      age: { $gt: +process.argv[2] }
    }, function(err, c){
      if(err) throw err;
      console.log(c);
    });
  dbobj.close();
});


//Solution 7
const url = 'mongodb://localhost:27017/learnyoumongo';
const mongo = require('mongodb').MongoClient;
mongo.connect(url, function(err, dbobj){
  if(err) throw err;
  const lym = dbobj.db(process.argv[2]);
  var col = lym.collection(process.argv[3]);
  col.remove({
      _id: process.argv[4]
    }, function(err){
      if(err) throw err;
    })
  dbobj.close();
});



//Solution 6
const url = 'mongodb://localhost:27017/learnyoumongo';
const mongo = require('mongodb').MongoClient;
mongo.connect(url, function(err, dbobj){
  if(err) throw err;
  const lym = dbobj.db(process.argv[2]);
  var users = lym.collection('users');
  users.update({
      username: 'tinatime'
    }, {
      $set: {
        age: 40
      }
    }, function(err, data){
      if(err) throw err;
    })
  dbobj.close();
});



//Solution 5
var url = 'mongodb://localhost:27017/learnyoumongo';
var mongo = require('mongodb').MongoClient;
mongo.connect(url, function(err, db) {
  if (err) throw err;
  // db gives access to the database
  const myDb = db.db('learnyoumongo');
  var docs = myDb.collection('docs');
  var obj = {firstName: process.argv[2], lastName: process.argv[3]};
  docs.insert(obj, function(err, res){
    if(err) throw err;
    console.log(JSON.stringify(obj));
  });
  db.close();
});



//Solution 4
var url = 'mongodb://localhost:27017/learnyoumongo';
var mongo = require('mongodb').MongoClient;
mongo.connect(url, function(err, db) {
  if (err) throw err;
  // db gives access to the database
  const myDb = db.db('learnyoumongo');
  var parrots = myDb.collection('parrots');
  parrots.find({
    age: {
      $gt: parseInt(process.argv[2])
    }
  }, { fields: {
    name: 1,
    age: 1,
    _id: 0

  }}).toArray(function(err, documents) {
    // Here is where we decide what to do with the query results
    if (err) throw err;
    console.log(documents);
    db.close();
  });
});



//Solution 3
var mongo = require('mongodb').MongoClient;
    mongo.connect('mongodb://localhost:27017/learnyoumongo', function(err, db) {
        if(err) throw err;
        const myDb = db.db('learnyoumongo');
        var parrots = myDb.collection('parrots');
        parrots.find({
            age: { $gt: +process.argv[2] }
        }).toArray(function(err, docs){
            if(err) throw err;
            console.log(docs);
            db.close();
        });
});

Try yourself first then see here!