How to Make RESTful API with Node.js and Express?

Express JS, a web application framework for Node.js, provide an ideal environment for creating RESTful APIs

In this comprehensive guide, we’ll walk through the process of building a REST API with Node.js and Express.

Prerequisites

Before getting started with building a RESTful API using Node.js and Express, make sure you have the following prerequisites in place:

Node.js and npm: Ensure you have Node.js and npm (Node Package Manager) installed on your system. You can download them from the official website: Node.js Downloads.
Text Editor or IDE: Choose a code editor or integrated development environment (IDE) to write your code. Popular choices include Visual Studio Code, Sublime Text.

🚀 Getting Started:

Let’s start by creating a new Node.js project and setting up the environment.

Step 1: Initialize a Node.js Project

Open your terminal or command prompt and navigate to the directory where you want to create your project.

Run the following command to initialize a new Node.js project:

npm init

You will be prompted to provide information about your project. Follow the prompts to complete the initialization.

Step 2: Install Express

Now that your project is initialized, you need to install the Express framework. Run the following command to install Express as a project dependency:

npm install express

This will download and install the Express package.

Step 3: Create the Main Application File

Create a new file in your project directory, typically named app.js or index.js. This file will serve as the main entry point for your application.

In this file, you need to require Express, create an instance of the application, and set up a basic route. Here’s a minimal example:

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

// Parsing incoming requests
app.use(express.json());

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

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

Step 4: Start the Application

You can now start your Node.js application by running the following command in your terminal:

node app.js

Your application should be running on the specified port (or the default port 3000). You can access it by opening a web browser and navigating to http://localhost:3000. You should see the “Hello, World!” message.

👷 Building a RESTful API:

Now that you have a basic Express application up and running, it’s time to create a RESTful API.

Step 1: Define API Routes

In a RESTful API, routes correspond to resources, and HTTP methods define actions on these resources. Here’s an example of defining routes for a simple REST API:

// Define a list of items
const items = [
  { id: 1, name: 'Item 1' },
  { id: 2, name: 'Item 2' },
  { id: 3, name: 'Item 3' },
];

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

// Get a single item by ID
app.get('/api/items/:id', (req, res) => {
  const itemId = parseInt(req.params.id);
  const item = items.find(i => i.id === itemId);

  if (!item) {
    return res.status(404).json({ message: 'Item not found' });
  }

  res.json(item);
});

In this example, we’ve defined two routes: one to get all items and another to get a single item by ID.

Step 2: Handle HTTP Methods

In REST, HTTP methods such as GET, POST, PUT, and DELETE are used to perform actions on resources. You can define routes for these methods to create a full-fledged API.

// Add a new item (POST)
app.post('/api/items', (req, res) => {
  const newItem = req.body;
  items.push(newItem);
  res.status(201).json(newItem);
});

// Update an item (PUT)
app.put('/api/items/:id', (req, res) => {
  const itemId = parseInt(req.params.id);
  const updatedItem = req.body;

  const index = items.findIndex(i => i.id === itemId);
  if (index === -1) {
    return res.status(404).json({ message: 'Item not found' });
  }

  items[index] = updatedItem;
  res.json(updatedItem);
});

// Delete an item (DELETE)
app.delete('/api/items/:id', (req, res) => {
  const itemId = parseInt(req.params.id);
  const index = items.findIndex(i => i.id === itemId);

  if (index === -1) {
    return res.status(404).json({ message: 'Item not found' });
  }

  const deletedItem = items.splice(index, 1);
  res.json(deletedItem[0]);
});

These routes handle creating, updating, and deleting items using the HTTP methods POST, PUT, and DELETE, respectively.

Step 3: Test the API

Here is the Complete Code:

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

// Define a list of items
const items = [
    { id: 1, name: 'Item 1' },
    { id: 2, name: 'Item 2' },
    { id: 3, name: 'Item 3' },
];

// Parsing incoming requests
app.use(express.json());

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

// Get a single item by ID
app.get('/api/items/:id', (req, res) => {
    const itemId = parseInt(req.params.id);
    const item = items.find((i) => i.id === itemId);

    if (!item) {
        return res.status(404).json({ message: 'Item not found' });
    }

    res.json(item);
});

// Add a new item (POST)
app.post('/api/items', (req, res) => {
    const newItem = req.body;
    items.push(newItem);
    res.status(201).json(newItem);
});

// Update an item (PUT)
app.put('/api/items/:id', (req, res) => {
    const itemId = parseInt(req.params.id);
    const updatedItem = req.body;

    const index = items.findIndex((i) => i.id === itemId);
    if (index === -1) {
        return res.status(404).json({ message: 'Item not found' });
    }

    items[index] = updatedItem;
    res.json(updatedItem);
});

// Delete an item (DELETE)
app.delete('/api/items/:id', (req, res) => {
    const itemId = parseInt(req.params.id);
    const index = items.findIndex((i) => i.id === itemId);

    if (index === -1) {
        return res.status(404).json({ message: 'Item not found' });
    }

    const deletedItem = items.splice(index, 1);
    res.json(deletedItem[0]);
});

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

Restart your Node app.js and test your REST API.

To test your RESTful API, you can use tools like Postman, Insomnia, VS Code Thunder Client extension, etc.

# Get all items
Request (GET) - http://localhost:3000/api/items
Response (200):
[
    { "id": 1, "name": "Item 1" },
    { "id": 2, "name": "Item 2" },
    { "id": 3, "name": "Item 3" }
]

# Get a single item
Request (GET) - http://localhost:3000/api/items/1
Response (200) - {"id":1,"name":"Item 1"}

# Add a new item
Request (POST) - http://localhost:3000/api/items
Payload (JSON) - {"id":4, "name":"John"}
Response (201) - {"id":4, "name":"John"}

# Get all items (after adding a new item)
Response:
[
    { "id": 1, "name": "Item 1" },
    { "id": 2, "name": "Item 2" },
    { "id": 3, "name": "Item 3" },
    { "id": 4, "name": "John" }
]

# Update an item
Request (PUT) - http://localhost:3000/api/items/4
Payload (JSON) - {"id":4, "name":"Rahul"}
Response (200) - {"id":4, "name":"Rahul"}

# Get all items (after update the id 4)
Response:
[
    { "id": 1, "name": "Item 1" },
    { "id": 2, "name": "Item 2" },
    { "id": 3, "name": "Item 3" },
    { "id": 4, "name": "Rahul" }
]

# Delete an item
Request (DELETE) - http://localhost:3000/api/items/3
Response (200) - {"id":3, "name":"Item 3"}

# Get all items (after deleting the id 3)
Response:
[
    { "id": 1, "name": "Item 1" },
    { "id": 2, "name": "Item 2" },
    { "id": 4, "name": "Rahul" }
]

Conclusion:

Building a RESTful API with Node.js and Express is an easy and powerful way to create a backend for your web applications.

This guide provides a starting point for creating a RESTful API using Node and Express, and you can expand it by adding more things as per the requirement of the project like –

Using Database to store data
Error Handling and Validation
Authentication and Authorization
File Uploading. Etc.

Thank You… 🙏❤️❤️