JWT (JSON Web Token) authentication is a widely-used approach for securing web applications. It enables secure communication and identity verification, making it ideal for APIs. In this article, we’ll implement JWT authentication in a Node.js app using MongoDB for data storage.

Let's jump right in! 🚀

🚀 Table of Contents

1. What is JWT Authentication?
2. 🌱 Setting Up the Project
3. 🛠️ Connecting to MongoDB
4. 🔒 Environment Configuration with .env File
5. ⚙️ Setting Up the Express App
6. 👤 Creating the User Model
7. 🔑 Building Authentication Routes
8. 🛡️ Securing Routes with Middleware
9. 📊 Testing the API

What is JWT Authentication?

JWT authentication uses JSON Web Tokens to verify user identity within a web app. A JWT consists of three parts:

1. Header: Contains the token type and encryption method.
2. Payload: Stores user-specific information, such as username and role.
3. Signature: Verifies the token's validity, ensuring data integrity.

The token is presented by users to access resources, acting as proof of their identity.

Step 1: 🌱 Setting Up the Project

To get started, create a new directory and initialize the project:

mkdir nodejs-jwt-auth
cd nodejs-jwt-auth
npm init -y

Install the required dependencies:

npm install express mongoose jsonwebtoken dotenv

• express: Framework for building web servers.
• mongoose: MongoDB library for handling data models.
• jsonwebtoken: Library for generating and verifying JWTs.
• dotenv: Manages environment variables securely.

Step 2: 🛠️ Connecting to MongoDB

Use MongoDB Atlas for cloud storage. Sign in to MongoDB Atlas and obtain your connection string.

In your .env file:

MONGODB_URL='mongodb+srv://your-username:your-password@cluster.mongodb.net/your-database'
SECRET_KEY='your_secret_key'

Replace the placeholders with your credentials.

Step 3: 🔒 Environment Configuration with .env File

Create a .env file to store your MongoDB URL and secret key for JWTs.

In .env:

MONGODB_URL='your-mongodb-connection-string'
SECRET_KEY='your-secret-key'

Step 4: ⚙️ Setting Up the Express App

Create index.js to configure Express and MongoDB connections:

const express = require("express");
const mongoose = require("mongoose");
require("dotenv").config();

const app = express();
const port = 3000;

app.use(express.json());

mongoose.connect(process.env.MONGODB_URL, {
  useNewUrlParser: true,
  useUnifiedTopology: true,
}).then(() => console.log("MongoDB connected"))
  .catch(error => console.error("Connection error", error));

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

Run the app:

node index.js

For automatic restarts, install nodemon:

npm install -g nodemon
nodemon index.js

Step 5: 👤 Creating the User Model

Define a User schema in models/User.js:

const mongoose = require("mongoose");

const userSchema = new mongoose.Schema({
  username: { type: String, required: true, unique: true },
  password: { type: String, required: true },
});

module.exports = mongoose.model("User", userSchema);

Step 6: 🔑 Building Authentication Routes

In routes/auth.js, define signup and login routes for creating users and generating JWT tokens.

const express = require("express");
const jwt = require("jsonwebtoken");
const User = require("../models/User");

const router = express.Router();

router.post("/signup", async (req, res) => {
  try {
    const { username, password } = req.body;
    const user = new User({ username, password });
    await user.save();
    res.status(201).json({ message: "User registered successfully" });
  } catch (error) {
    res.status(500).json({ message: "Internal Server Error" });
  }
});

router.post("/login", async (req, res) => {
  const { username, password } = req.body;
  try {
    const user = await User.findOne({ username });
    if (!user || user.password !== password) {
      return res.status(401).json({ message: "Invalid credentials" });
    }

    const token = jwt.sign({ id: user._id, username: user.username }, process.env.SECRET_KEY);
    res.json({ token });
  } catch (error) {
    res.status(500).json({ message: "Internal Server Error" });
  }
});

module.exports = router;

Step 7: 🛡️ Securing Routes with Middleware

Create a middleware.js file to verify JWTs:

const jwt = require("jsonwebtoken");

function verifyJWT(req, res, next) {
  const token = req.headers["authorization"];
  if (!token) {
    return res.status(401).json({ message: "Access denied" });
  }

  jwt.verify(token, process.env.SECRET_KEY, (err, user) => {
    if (err) {
      return res.status(403).json({ message: "Invalid token" });
    }
    req.user = user;
    next();
  });
}

module.exports = verifyJWT;

Step 8: 📊 Testing the API

1. Signup: POST to /auth/signup with a JSON body:
   

   { "username": "john_doe", "password": "securepass" }
   

2. Login: POST to /auth/login with the same credentials:
   

   { "username": "john_doe", "password": "securepass" }
   

3. Accessing Protected Route: Send a GET request to /protected with the JWT token in the Authorization header.

Congratulations! You’ve now successfully implemented JWT authentication in a Node.js app. This setup secures your API routes, allowing only authenticated users to access them.

That's all for today.

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