Express.js API Creation Examples

Introduction to Express.js

Express.js is a minimal and flexible Node.js web application framework that provides a robust set of features for building web and mobile applications. It simplifies the process of creating APIs by providing a straightforward way to handle HTTP requests and responses. Below, you’ll find three practical examples of using Express.js to simplify API creation, perfect for beginners and intermediate developers alike.

Example 1: Creating a Simple RESTful API for Users

Use Case

This example demonstrates how to set up a basic RESTful API to manage user data. This is a common requirement in many applications where you need to handle user information like name, email, and age.

Example Code

const express = require('express');
const app = express();
const PORT = 3000;

app.use(express.json()); // Middleware to parse JSON bodies

let users = [];

// Create a new user
app.post('/users', (req, res) => {
    const { name, email, age } = req.body;
    const newUser = { id: users.length + 1, name, email, age };
    users.push(newUser);
    res.status(201).json(newUser);
});

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

// Get a user by ID
app.get('/users/:id', (req, res) => {
    const user = users.find(u => u.id === parseInt(req.params.id));
    if (!user) return res.status(404).send('User not found');
    res.json(user);
});

app.listen(PORT, () => {
    console.log(`Server is running on http://localhost:${PORT}`);
});

Notes

• This example uses an in-memory array to store users, which means data will be lost when the server restarts. For a production application, consider using a database.
• You can easily expand this API by adding more endpoints for updating and deleting users.

Example 2: Building a To-Do List API

Use Case

In this example, we will create a simple API to manage a to-do list. This API allows users to create, read, update, and delete tasks, which is a common feature in many applications.

Example Code

const express = require('express');
const app = express();
const PORT = 3000;

app.use(express.json());

let todos = [];

// Create a new to-do
app.post('/todos', (req, res) => {
    const { title, completed } = req.body;
    const newTodo = { id: todos.length + 1, title, completed: completed || false };
    todos.push(newTodo);
    res.status(201).json(newTodo);
});

// Get all to-dos
app.get('/todos', (req, res) => {
    res.json(todos);
});

// Update a to-do
app.put('/todos/:id', (req, res) => {
    const todo = todos.find(t => t.id === parseInt(req.params.id));
    if (!todo) return res.status(404).send('To-do not found');
    todo.title = req.body.title || todo.title;
    todo.completed = req.body.completed !== undefined ? req.body.completed : todo.completed;
    res.json(todo);
});

// Delete a to-do
app.delete('/todos/:id', (req, res) => {
    todos = todos.filter(t => t.id !== parseInt(req.params.id));
    res.status(204).send();
});

app.listen(PORT, () => {
    console.log(`Server is running on http://localhost:${PORT}`);
});

Notes

• This API provides full CRUD functionality for managing to-do items.
• Consider adding validation to ensure that the incoming data is correct before processing it.

Example 3: Simple API for a Book Store

Use Case

This example sets up a basic API for a book store. It allows users to manage a list of books, which is useful for applications related to reading, libraries, or e-commerce.

Example Code

const express = require('express');
const app = express();
const PORT = 3000;

app.use(express.json());

let books = [];

// Add a new book
app.post('/books', (req, res) => {
    const { title, author, year } = req.body;
    const newBook = { id: books.length + 1, title, author, year };
    books.push(newBook);
    res.status(201).json(newBook);
});

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

// Get a book by ID
app.get('/books/:id', (req, res) => {
    const book = books.find(b => b.id === parseInt(req.params.id));
    if (!book) return res.status(404).send('Book not found');
    res.json(book);
});

app.listen(PORT, () => {
    console.log(`Server is running on http://localhost:${PORT}`);
});

Notes

• This API is a great starting point for building a more complex book management system.
• You can extend it with features like sorting, filtering, or searching for books based on various criteria.

Conclusion

These examples of using Express.js to simplify API creation illustrate how easy it is to set up a functional API with just a few lines of code. Whether you’re managing users, to-do lists, or books, Express.js provides a powerful and flexible framework to get you started. Happy coding!