Learning Backend – Part 2: Building a REST API with Express.js

This guide provides instructions for establishing an Express.js server configured for a REST API. We'll cover setup requirements, deployment steps, and guidance for constructing GET and POST endpoints.

What is Express.js?

Express.js is a minimal and flexible Node.js web application framework that provides a robust set of features for web and mobile applications. It's the most popular Node.js framework for building REST APIs.

Setup Requirements

Before we begin, ensure you have:

• Node.js installed (v14 or higher)
• npm or yarn package manager
• A code editor (VS Code recommended)
• Basic understanding of JavaScript and HTTP methods

Project Initialization

Let's start by creating a new Express.js project:

mkdir my-rest-api
cd my-rest-api
npm init -y
npm install express

Creating Your First Server

Create an index.js file and set up a basic Express server:

const express = require('express');
const app = express();
const PORT = process.env.PORT || 3000;

// Middleware
app.use(express.json());

// Basic route
app.get('/', (req, res) => {
  res.json({ message: 'Welcome to my REST API' });
});

app.listen(PORT, () => {
  console.log(`Server running on port ${PORT}`);
});

Building GET Endpoints

Learn how to create GET endpoints to retrieve data:

// Get all items
app.get('/api/items', (req, res) => {
  // Return data
});

// Get single item by ID
app.get('/api/items/:id', (req, res) => {
  const { id } = req.params;
  // Return specific item
});

Building POST Endpoints

Create POST endpoints to accept and process data:

app.post('/api/items', (req, res) => {
  const newItem = req.body;
  // Process and save data
  res.status(201).json(newItem);
});

Middleware

Understanding and implementing middleware for:

• Request logging
• Error handling
• Body parsing
• CORS support

Testing Your API

Use testing utilities to verify your endpoints:

• Postman for manual testing
• Thunder Client (VS Code extension)
• curl commands
• Automated testing with Jest

Best Practices

• Use proper HTTP status codes
• Implement error handling middleware
• Validate request data
• Use environment variables
• Follow RESTful naming conventions

Future Integration Opportunities

In the next parts, we'll cover:

• Database connectivity with PostgreSQL
• Authentication and authorization
• Security measures (CORS, rate limiting)
• API documentation with Swagger

Conclusion

You've now built a basic REST API with Express.js! This foundation will help you create more complex backend applications with database integration and security features.