How to Connect to MongoDB with Mongoose

Table Of Contents

• Problem
• Solution
• Explanation

Problem

You need to connect your Node.js application to a MongoDB database using Mongoose for data operations and schema management.

Solution

const mongoose = require('mongoose');

// Basic connection
async function connectMongoDB() {
  try {
    await mongoose.connect('mongodb://localhost:27017/myapp', {
      useNewUrlParser: true,
      useUnifiedTopology: true
    });
    
    console.log('Connected to MongoDB');
  } catch (error) {
    console.error('MongoDB connection error:', error);
    process.exit(1);
  }
}

// Connection with options
async function connectWithOptions() {
  const options = {
    useNewUrlParser: true,
    useUnifiedTopology: true,
    maxPoolSize: 10,
    serverSelectionTimeoutMS: 5000,
    socketTimeoutMS: 45000,
  };
  
  await mongoose.connect(process.env.MONGODB_URI || 'mongodb://localhost:27017/myapp', options);
}

// Connection event handlers
mongoose.connection.on('connected', () => {
  console.log('Mongoose connected to MongoDB');
});

mongoose.connection.on('error', (error) => {
  console.error('Mongoose connection error:', error);
});

mongoose.connection.on('disconnected', () => {
  console.log('Mongoose disconnected');
});

// Graceful shutdown
process.on('SIGINT', async () => {
  await mongoose.connection.close();
  console.log('MongoDB connection closed');
  process.exit(0);
});

// Simple schema example
const userSchema = new mongoose.Schema({
  name: String,
  email: String,
  createdAt: { type: Date, default: Date.now }
});

const User = mongoose.model('User', userSchema);

Install Mongoose:

npm install mongoose

Explanation

Use mongoose.connect() with your MongoDB connection string. The connection is asynchronous, so wrap it in try-catch for error handling.

Set up event listeners for connection states and implement graceful shutdown to properly close the database connection when your app terminates.