Next.js is a popular React framework that enables developers to build fast, SEO-friendly, and scalable web applications. It offers powerful features like server-side rendering, static site generation, and API routes, making it an excellent choice for modern web development. In this step-by-step guide, we'll walk through the process of building your first Next.js application from scratch.

Step 1: Setting Up Your Development Environment

Before we start building, ensure you have Node.js and npm (or Yarn) installed on your machine. You can download and install them from Node.js.

Step 2: Create a New Next.js Application

Next.js provides a boilerplate generator that makes it easy to start a new project. Run the following command to create a new Next.js application:

npx create-next-app my-next-app

Replace my-next-app with your desired project name. This command sets up a new Next.js project with all the necessary files and dependencies.

Step 3: Run the Development Server

Navigate to your project directory and start the development server:

cd my-next-app
npm run dev

Your application should now be running at http://localhost:3000. Open this URL in your browser to see the default Next.js welcome page.

Step 4: Create Your First Page

Next.js uses a file-based routing system where each file in the pages directory corresponds to a route in your application. Let's create a new page called about.js.

1. Create a new file in the pages directory:

touch pages/about.js

2. Add the following content to pages/about.js:

// pages/about.js
const About = () => {
  return (
    <div>
      <h1>About Us</h1>
      <p>Welcome to the about page of our Next.js application.</p>
    </div>
  );
};

export default About;

You can now navigate to http://localhost:3000/about to see your new About page.

Step 5: Adding a Navigation Menu

To navigate between pages, let's add a simple navigation menu to our application. We'll do this by creating a layout component.

1. Create a new directory called components:

mkdir components

2. Create a new file called components/Layout.js and add the following content:

// components/Layout.js
import Link from 'next/link';

const Layout = ({ children }) => {
  return (
    <div>
      <nav>
        <ul>
          <li>
            <Link href="/">Home</Link>
          </li>
          <li>
            <Link href="/about">About</Link>
          </li>
        </ul>
      </nav>
      <main>{children}</main>
    </div>
  );
};

export default Layout;

3. Wrap your pages with the Layout component. Modify pages/index.js as follows:

// pages/index.js
import Layout from '../components/Layout';

const Home = () => {
  return (
    <Layout>
      <h1>Home Page</h1>
      <p>Welcome to our Next.js application.</p>
    </Layout>
  );
};

export default Home;

4. Update pages/about.js to use the Layout component:

// pages/about.js
import Layout from '../components/Layout';

const About = () => {
  return (
    <Layout>
      <h1>About Us</h1>
      <p>Welcome to the about page of our Next.js application.</p>
    </Layout>
  );
};

export default About;

Step 6: Fetching Data with getStaticProps

Next.js supports static site generation, allowing you to fetch data at build time. Let's create a page that fetches and displays a list of posts.

1. Create a new file called pages/posts.js:

touch pages/posts.js

2. Add the following content to pages/posts.js:

// pages/posts.js
import Layout from '../components/Layout';

export const getStaticProps = async () => {
  const res = await fetch('https://jsonplaceholder.typicode.com/posts');
  const posts = await res.json();

  return {
    props: {
      posts,
    },
  };
};

const Posts = ({ posts }) => {
  return (
    <Layout>
      <h1>Posts</h1>
      <ul>
        {posts.map(post => (
          <li key={post.id}>
            <h2>{post.title}</h2>
            <p>{post.body}</p>
          </li>
        ))}
      </ul>
    </Layout>
  );
};

export default Posts;

Now, navigate to http://localhost:3000/posts to see the list of posts fetched from the API.

Step 7: Adding API Routes

Next.js allows you to create API routes within your application. These routes can be used to handle backend logic, database interactions, or third-party API requests.

1. Create a new directory called pages/api.

mkdir pages/api

2. Create a new file called pages/api/hello.js:

touch pages/api/hello.js

3. Add the following content to pages/api/hello.js:

// pages/api/hello.js
export default function handler(req, res) {
  res.status(200).json({ message: 'Hello from Next.js API!' });
}

You can now access this API endpoint at http://localhost:3000/api/hello.

This guide covers the basics, but Next.js has many more features to explore. Check out the official Next.js documentation for more advanced topics and best practices. Happy coding!