Rakesh Bisht

Posted on Sep 14

MongoDB for Node.js Developers - The Quick Guide

#mongodb #node #webdev #javascript

Getting Started (Takes 2 minutes)

First things first - let's get MongoDB installed in your project:

# Just run this in your terminal
npm install mongodb

That's it! You're ready to go.

Connecting to Your Database

Here's how I usually set up my MongoDB connection. Pretty straightforward:

const { MongoClient } = require('mongodb');

// Your database URL - change this to match your setup
const uri = 'mongodb://localhost:27017';
const client = new MongoClient(uri);

async function connectToDatabase() {
  try {
    await client.connect();
    console.log('Hey, we\'re connected!');

    const db = client.db('myapp');
    const users = db.collection('users');

    // Do your stuff here

  } catch (error) {
    console.log('Oops, connection failed:', error);
  } finally {
    await client.close();
  }
}

The Big Four: Create, Read, Update, Delete

Adding New Data (Create)

// Adding one user
const newUser = await users.insertOne({ 
  name: 'Sarah', 
  email: 'sarah@example.com', 
  age: 28 
});
console.log('New user added! ID:', newUser.insertedId);

// Adding multiple users at once - super handy
const manyUsers = await users.insertMany([
  { name: 'Mike', email: 'mike@example.com', age: 32 },
  { name: 'Emma', email: 'emma@example.com', age: 26 }
]);
console.log(`Added ${manyUsers.insertedCount} users`);

Getting Your Data Back (Read)

// Get everyone
const everyone = await users.find({}).toArray();

// Find just one person
const person = await users.findOne({ name: 'Sarah' });

// Find people over 18 (because why not)
const adults = await users.find({ age: { $gte: 18 } }).toArray();

// Get the top 5 oldest users, sorted
const oldestUsers = await users
  .find({})
  .sort({ age: -1 })
  .limit(5)
  .toArray();

// Sometimes you don't need everything - just grab names and emails
const contacts = await users
  .find({}, { projection: { name: 1, email: 1, _id: 0 } })
  .toArray();

Updating Existing Data

// Change one person's age
const updated = await users.updateOne(
  { name: 'Sarah' },
  { $set: { age: 29 } }
);
console.log(`Updated ${updated.modifiedCount} person`);

// Update everyone under 18 (set them as minors)
await users.updateMany(
  { age: { $lt: 18 } },
  { $set: { status: 'minor' } }
);

// Replace someone's entire record (keeping the same ID)
await users.replaceOne(
  { name: 'Sarah' },
  { 
    name: 'Sarah Johnson', 
    email: 'sarah.johnson@example.com', 
    age: 29,
    city: 'Boston'
  }
);

Removing Data (Delete)

// Remove one person
const removed = await users.deleteOne({ name: 'Sarah' });
console.log(`Removed ${removed.deletedCount} person`);

// Remove all minors (careful with this one!)
await users.deleteMany({ age: { $lt: 18 } });

Some Useful Query Tricks

// Find people named John OR Jane
const result = await users.find({
  $or: [
    { name: 'John' },
    { name: 'Jane' }
  ]
}).toArray();

// Count how many adults you have
const adultCount = await users.countDocuments({ age: { $gte: 18 } });

// Check if someone exists (returns true/false)
const userExists = await users.findOne({ email: 'sarah@example.com' }) !== null;

// Get all unique ages in your database
const uniqueAges = await users.distinct('age');

A Complete Working Example

This is what I typically use as a starting point:

const { MongoClient } = require('mongodb');

async function runExample() {
  const uri = 'mongodb://localhost:27017';
  const client = new MongoClient(uri);

  try {
    // Connect
    await client.connect();
    console.log('Connected successfully!');

    const db = client.db('myapp');
    const users = db.collection('users');

    // Add a new user
    const newUser = await users.insertOne({
      name: 'Alex Smith',
      email: 'alex@example.com',
      age: 25,
      createdAt: new Date()
    });
    console.log('Created user:', newUser.insertedId);

    // Find all adults
    const adults = await users.find({ age: { $gte: 18 } }).toArray();
    console.log(`Found ${adults.length} adults`);

    // Update Alex's age
    const updateResult = await users.updateOne(
      { email: 'alex@example.com' }, 
      { $set: { age: 26 } }
    );
    console.log('Updated Alex\'s age');

    // Clean up - remove Alex
    const deleteResult = await users.deleteOne({ email: 'alex@example.com' });
    console.log('Removed Alex from database');

  } catch (error) {
    console.log('Something went wrong:', error);
  } finally {
    await client.close();
    console.log('Connection closed');
  }
}

runExample();

MongoDB Query Cheat Sheet

These are the operators I use most often:

// Basic comparisons
{ age: { $gt: 18 } }        // older than 18
{ age: { $gte: 18 } }       // 18 or older  
{ age: { $lt: 65 } }        // younger than 65
{ age: { $ne: 30 } }        // not 30 years old
{ age: { $in: [25, 30, 35] } }  // age is 25, 30, or 35

// Text searches
{ name: { $regex: 'sarah', $options: 'i' } }  // case-insensitive
{ email: { $exists: true } }                  // has email field

// Combining conditions
{ $and: [{ age: { $gte: 18 } }, { age: { $lt: 65 } }] }  // between 18-65
{ $or: [{ name: 'John' }, { name: 'Jane' }] }            // John OR Jane

Working with Arrays and Updates

// Update operators I use regularly
{ $set: { age: 30 } }              // set a value
{ $inc: { age: 1 } }               // add 1 to age
{ $unset: { oldField: '' } }       // remove a field
{ $push: { hobbies: 'reading' } }  // add to array
{ $pull: { hobbies: 'gaming' } }   // remove from array
{ $currentDate: { lastSeen: true } }  // set current timestamp

Better Connection Management

Here's a cleaner way to handle database connections:

class Database {
  constructor(uri = 'mongodb://localhost:27017', dbName = 'myapp') {
    this.client = new MongoClient(uri);
    this.dbName = dbName;
    this.db = null;
  }

  async connect() {
    await this.client.connect();
    this.db = this.client.db(this.dbName);
    console.log('Database connected');
    return this.db;
  }

  async disconnect() {
    await this.client.close();
    console.log('Database disconnected');
  }

  collection(name) {
    return this.db.collection(name);
  }
}

// Use it like this:
const database = new Database();
await database.connect();

const users = database.collection('users');
// do your operations...

await database.disconnect();

Things to Remember

Always use await with database operations (they're asynchronous)
Don't forget .toArray() when using find() - it returns a cursor, not an array
Close your connections when you're done - client.close()
Handle errors properly with try-catch blocks
When querying large datasets, consider using projections to only get the fields you need

That covers pretty much everything you'll need for day-to-day MongoDB work with Node.js. Start with the basics and build from there - you'll be surprised how much you can accomplish with just these operations!

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