README.md

User API - Node.js Express + MongoDB

A simple Node.js Express API that connects to MongoDB and retrieves user data with age filtering.

Approach

This API implements a GET endpoint that queries MongoDB for users by ID, with the unique requirement of only returning users over 21 years old. The solution includes proper error handling for invalid ObjectIds and comprehensive validation to ensure data integrity.

Features

• ✅ GET /users/:id endpoint with age filtering (> 21)
• ✅ MongoDB integration with proper connection handling
• ✅ ObjectId validation with graceful error handling
• ✅ 404 responses for non-existent users or users ≤ 21
• ✅ Environment variable configuration
• ✅ Health check endpoint

Prerequisites

• Node.js (v14 or higher)
• MongoDB (local or cloud instance)
• npm or yarn

Installation

1. Clone the repository:

git clone <your-repo-url>
cd user-api

2. Install dependencies:

npm install

3. Set up environment variables:

cp env.example .env
# Edit .env with your MongoDB connection details

4. Start the server:

# Development mode with auto-restart
npm run dev

# Production mode
npm start

API Endpoints

GET /users/:id

Retrieves a user by ID, only if they are over 21 years old.

Parameters:

• id (string): MongoDB ObjectId of the user

Responses:

• 200 OK: User found and over 21
• 400 Bad Request: Invalid ObjectId format
• 404 Not Found: User not found or user is 21 or younger
• 500 Internal Server Error: Server error

Example Request:

curl http://localhost:3000/users/507f1f77bcf86cd799439011

Example Response:

{
  "_id": "507f1f77bcf86cd799439011",
  "name": "John Doe",
  "email": "johndoe@email.com",
  "age": 30
}

GET /health

Health check endpoint to verify server status.

Example Response:

{
  "status": "OK",
  "message": "Server is running"
}

MongoDB Schema

The API expects a users collection with the following schema:

{
  "_id": ObjectId,
  "name": "John Doe",
  "email": "johndoe@email.com",
  "age": 30
}

Sample Data Setup

You can insert sample data into your MongoDB users collection:

db.users.insertMany([
  {
    name: "John Doe",
    email: "johndoe@email.com",
    age: 30
  },
  {
    name: "Jane Smith",
    email: "janesmith@email.com",
    age: 25
  },
  {
    name: "Bob Johnson",
    email: "bobjohnson@email.com",
    age: 19
  }
]);

Error Handling

The API includes comprehensive error handling:

• Invalid ObjectId: Returns 400 with descriptive error message
• User not found: Returns 404 with explanation
• User ≤ 21: Returns 404 (treated as "not found" due to age filter)
• Database errors: Returns 500 with generic error message

Environment Variables

Variable	Description	Default
MONGODB_URI	MongoDB connection string	mongodb://localhost:27017
DB_NAME	Database name	userdb
PORT	Server port	3000

Development

To run in development mode with auto-restart:

npm run dev

License

MIT