What is Mongoose and how do you use it? | MongoDB Interview Questions

What You'll Learn

What Mongoose is
Defining schemas
Basic operations

What is Mongoose?

Mongoose is an ODM (Object Document Mapper) for MongoDB and Node.js. It provides schema validation and a cleaner API.

Setup

code.jsJavaScript

const mongoose = require('mongoose');

mongoose.connect('mongodb://localhost:27017/mydb');

Define Schema and Model

code.jsJavaScript

const userSchema = new mongoose.Schema({
  name: { type: String, required: true },
  email: { type: String, required: true, unique: true },
  age: { type: Number, min: 0 },
  role: { type: String, enum: ['user', 'admin'], default: 'user' },
  createdAt: { type: Date, default: Date.now }
});

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

CRUD Operations

code.jsJavaScript

// Create
const user = await User.create({ name: 'John', email: 'john@example.com' });
// or
const user = new User({ name: 'John', email: 'john@example.com' });
await user.save();

// Read
const users = await User.find({ role: 'admin' });
const user = await User.findById(id);
const user = await User.findOne({ email: 'john@example.com' });

// Update
await User.findByIdAndUpdate(id, { name: 'John Updated' }, { new: true });
await User.updateMany({ role: 'user' }, { $set: { active: true } });

// Delete
await User.findByIdAndDelete(id);
await User.deleteMany({ active: false });

Query Helpers

code.jsJavaScript

const users = await User
  .find({ age: { $gte: 18 } })
  .select('name email')
  .sort({ createdAt: -1 })
  .limit(10)
  .skip(20);