Next.js - Implementing User Authentication

Introduction

User authentication is a crucial aspect of most web applications today. With Next.js, we can easily implement user authentication using a variety of authentication strategies.

In this guide, we will implement user authentication using the JWT (JSON Web Token) strategy with Next.js.

Requirements

Before we get started, we’ll need to have the following:

• Basic knowledge of Next.js and React.
• An understanding of how user authentication works.
• A backend API that can generate and verify JWT tokens.

Steps

Here are the steps you can follow to implement user authentication with Next.js:

1. Create a custom _app.js file in the pages folder.
2. Add the necessary packages, including jsonwebtoken and universal-cookie.
3. Implement the logic for generating and saving JWT tokens in the browser.
4. Create a simple login form that takes in credentials and requests a JWT token.
5. Add authentication checks to components and pages that require authentication.

Explanation

1. Custom _app.js file: A custom _app.js file allows you to apply global styles and layouts to all pages in your Next.js application. We'll use it to initialize our authentication logic before any components are rendered.
2. Packages: We need to install jsonwebtoken and universal-cookie. jsonwebtoken allows us to generate and verify JWT tokens, while universal-cookie allows us to set, get, and remove cookies on the client-side and server-side.
3. JWT token generation and storage: We generate JWT tokens on the backend and store them in a cookie on the client-side. We need to implement a function that can check if a user is authenticated based on the validity of the JWT token.
4. Login form: We’ll create a simple login form that takes in credentials and sends a request to the backend API to retrieve a token.
5. Authentication checks: We need to add authentication checks to components and pages that require authentication. If a user is not authenticated, they should be redirected to the login page.

Example

Here is an example of how you can implement user authentication with Next.js using JWT tokens:

import jwt from 'jsonwebtoken';
import Cookies from 'universal-cookie';

const cookies = new Cookies();

export function GetToken() {
  const token = cookies.get('token');
  if (!token) return null;
  try {
    const decoded = jwt.verify(token, process.env.JWT_SECRET);
    return decoded;
  } catch (err) {
    cookies.remove('token');
    return null;
  }
}

import { GetToken } from 'path/to/file';

function PrivatePage(props) {
  const user = GetToken();
  if (!user) {
    return <div>You are not authorized to access this page.</div>
  }
  return <div>Hello {user.name}!</div>
}

Use

• Use this guide to learn how to implement user authentication with Next.js using JWT tokens.
• Use this guide to learn how to use jsonwebtoken and universal-cookie packages to generate and store JWT tokens.
• Use this guide to add authentication checks to components and pages that require authentication.

Important Points

• Always use a secure backend API to generate and verify JWT tokens.
• Always store JWT tokens in a secure manner.
• Use cookies to store JWT tokens in the client-side browser.
• Use jsonwebtoken and universal-cookie packages to generate and store JWT tokens.

Summary

With Next.js, implementing user authentication with JWT tokens is relatively straightforward. We can use jsonwebtoken and universal-cookie packages to generate and store JWT tokens. Then, we can implement a custom _app.js file to initialize our authentication logic before any components are rendered. Finally, we can add authentication checks to components and pages that require authentication.