Building a REST API with Express.js

1. Introduction

In this tutorial, we will explore how to build a RESTful API using Express.js. APIs (Application Programming Interfaces) are used to allow different software systems to communicate with each other. Express.js is a web application framework for Node.js, designed to build web applications and APIs.

What You'll Learn

• Understanding REST APIs
• Setting up Express.js
• Building and configuring an API
• Creating endpoints for CRUD operations

Prerequisites

• Basic understanding of JavaScript
• Familiarity with Node.js

2. Step-by-Step Guide

Installing Express.js

Express.js is a Node.js package; therefore, we will be using npm (Node Package Manager) to install it. If you haven't installed Node.js, you can download it here.

# Create a new directory and initialize it with npm init
mkdir express-api && cd express-api
npm init -y

# Install express
npm install express

Creating Your First Route

Express.js uses routes to handle requests. A route is a combination of a URL pattern and a HTTP method (e.g., GET, POST, PUT, DELETE).

const express = require('express');
const app = express();

app.get('/', (req, res) => {
  res.send('Hello World!');
});

app.listen(3000, () => {
  console.log('App is running on http://localhost:3000');
});

3. Code Examples

Example: Creating a GET Endpoint

We will create a /movies GET endpoint that will return a list of movies.

let movies = [
  { id: 1, title: 'Inception', director: 'Christopher Nolan' },
  { id: 2, title: 'Interstellar', director: 'Christopher Nolan' },
];

app.get('/movies', (req, res) => {
  res.json(movies);
});

Example: Creating a POST Endpoint

We will create a /movies POST endpoint to add a new movie.

app.use(express.json()); // Enable JSON body parsing

app.post('/movies', (req, res) => {
  const newMovie = req.body;
  movies.push(newMovie);
  res.json(newMovie);
});

4. Summary

In this tutorial, we have covered:
- What REST APIs are
- How to set up Express.js
- How to build and configure an API
- How to create endpoints for CRUD operations

To continue learning, consider diving deeper into Express.js middlewares, error handling, and more advanced features. Here are some resources:
- Express.js Official Documentation
- REST API Tutorial

5. Practice Exercises

1. Create a DELETE endpoint for movies

2. The endpoint should accept a movie ID and remove the corresponding movie from the list.

3. Create a PUT endpoint for movies

4. The endpoint should accept a movie ID and a new movie object. It should replace the existing movie with the new one.

Solutions:

1. DELETE Endpoint

app.delete('/movies/:id', (req, res) => {
  const { id } = req.params;
  movies = movies.filter(movie => movie.id != id);
  res.json({ message: 'Movie deleted' });
});

1. PUT Endpoint

app.put('/movies/:id', (req, res) => {
  const { id } = req.params;
  const newMovie = req.body;

  movies = movies.map(movie => movie.id == id ? newMovie : movie);
  res.json(newMovie);
});

Remember to test your endpoints using tools like Postman or curl. Keep practicing and happy coding!