Introduction

REST APIs (Representational State Transfer) are a popular way to expose backend data to frontend applications. Using Express.js, a lightweight Node.js framework, and MongoDB, a NoSQL database, we can build a scalable, efficient backend service.

Prerequistes

• Basic knowledge of JavaScript and Node.js
• Node.js and npm installed
• MongoDB installed locally or access to MongoDB Atlas

Project Setup

1. Initialize the project:

   mkdir rest-api && cd rest-api
   npm init -y
   

2. Install dependencies

   npm install express mongoose dotenv
   

3. Create folder structure

   rest-api/
   |-- controllers/
   |-- models/
   |-- routes/
   |-- .env
   |-- server.js
   |-- config/
   

4. Setting up Express Server (server.js)

   const express = require('express');
   const mongoose = require('mongoose');
   const dotenv = require('dotenv');
   const userRoutes = require('./routes/userRoutes');
   
   dotenv.config();
   const app = express();
   
   // Middleware
   app.use(express.json());
   
   // Routes
   app.use('/api/users', userRoutes);
   
   // Connect to MongoDB
   mongoose.connect(process.env.MONGO_URI)
   .then(() => console.log("MongoDB connected"))
   .catch(err => console.log(err));
   
   const PORT = process.env.PORT || 5000;
   app.listen(PORT, () => console.log(`Server running on port ${PORT}`));
   

5. MongoDB Model (models/User.js)

   const mongoose = require('mongoose');
   const userSchema = new mongoose.Schema({
   name: { type: String, required: true },
   email: { type: String, required: true, unique: true },
   age: Number
   }, { timestamps: true });
   
   module.exports = mongoose.model('User', userSchema);
   

6. Controller Functions (controllers/userController.js)

   const User = require('../models/User');
   
   // GET all users
   exports.getUsers = async (req, res) => {
   const users = await User.find();
   res.json(users);
   };
   
   // POST create new user
   exports.createUser = async (req, res) => {
   const newUser = new User(req.body);
   await newUser.save();
   res.status(201).json(newUser);
   };
   
   // GET user by ID
   exports.getUserById = async (req, res) => {
   const user = await User.findById(req.params.id);
   user ? res.json(user) : res.status(404).json({ message: 'User not found' });
   };
   
   // PUT update user
   exports.updateUser = async (req, res) => {
   const user = await User.findByIdAndUpdate(req.params.id, req.body, { new: true });
   user ? res.json(user) : res.status(404).json({ message: 'User not found' });
   };
   
   // DELETE user
   exports.deleteUser = async (req, res) => {
   const user = await User.findByIdAndDelete(req.params.id);
   user ? res.json({ message: 'User deleted' }) : res.status(404).json({ message: 'User not found' });
   };
   

Sample API Endpoints

• Get all users

  Method: GET

  Endpoints: /api/users

• Get user by id

  Method: GET

  Endpoints: /api/users/:id

• Create a user

  Method: POST

  Endpoints: /api/users

• Update user by id

  Method: PUT

  Endpoints: /api/users/:id

• Delete user by id

  Method: DELETE

  Endpoints: /api/users/:id

Testing the API

you can test the API using tools like:

• Postman
• curl
• VS Code REST Client plugin

Conclusion

With Express.js and MongoDB, building a REST API becomes straightforward and efficient. You can easily extend this foundation to include:

• Authentication (JWT)
• Pagination
• Input Validation
• Error handling Middleware
• Role-based access control