Getting Started with React and Next.js: A Beginner-Friendly Guide

Introduction

If you’ve been itching to dive into Next.js, but aren’t completely sure if your JavaScript or React foundations are strong enough, this post is for you. We’ve compiled key lessons from the React Foundations mini-course on https://nextjs.org/learn/react-foundations to give you a beginner-friendly, step-by-step guide to mastering React basics.

You’ll build a simple project, starting as a plain JavaScript application, then gradually moving on to React, and finally to Next.js. Each section builds on the previous one, ensuring you can jump in at your current comfort level—whether you only know HTML/CSS/JavaScript or are new to React altogether.

Here’s a brief overview of what you can expect:

React Foundations:

• Learn why a solid understanding of JavaScript and React benefits your Next.js journey.

• Discover how each section of this guide focuses on a different layer of building your React skills.

• See where you can seamlessly transition your knowledge into the world of Next.js—once you’re ready.

  
  

This blog post compiles the essential material from the React Foundations mini-course to give you a smooth learning experience, all in one place. Strap in, and let’s get started on your journey from JavaScript basics to full-fledged Next.js applications!

So if you’re new to React or curious about Next.js, this post is for you. We’ll go through the basics of how React works, how to build user interfaces (UI), and why Next.js can save you a lot of time and effort setting up modern web applications. By the end, you should have a clear sense of how React and Next.js fit together—and how to begin your own projects.

1. Building Modern Web Applications

Before diving into React, it’s useful to understand what goes into a web application. Generally, you need to think about:

• User Interface: How the page looks and how a user interacts with it.

• Routing: How users navigate between different URLs or sections.

• Data Fetching: Where your data lives (e.g., a database, an API) and how you get it.

• Rendering: When and where content is generated—on the server or the client.

• Integrations: How you connect third-party services like CMSs, payment platforms, or authentication.

• Infrastructure: Where and how you host your application code—serverless functions, CDNs, edge networks, etc.

• Performance & Scalability: Ensuring fast load times and handling traffic growth.

• Developer Experience: Making the process of building, updating, and debugging as efficient as possible.

  
  

React is a powerful UI library, but on its own, it doesn’t cover all these needs. Next.js fills in many of these gaps, giving you everything you need to develop robust, performant applications.

2. What Is React?

React is a JavaScript library for creating interactive user interfaces. Think of React as a collection of helpful functions and patterns that enable you to build reusable components (small, self-contained pieces of UI) that can be composed into larger applications.

Key points about React:

• JSX: React uses a syntax extension called JSX, which looks like HTML inside JavaScript. This makes it easier to describe what the UI should look like.

• Components: You build your interface using functions or classes (commonly just functions now) called components. Each component returns the part of the UI it’s responsible for.

• Unopinionated: React doesn’t enforce a specific folder structure or require certain libraries for things like routing or data fetching. This freedom is great for flexibility but also means you have more decisions to make.

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3. What Is Next.js?

Next.js is a React framework that handles many of the heavy lifting tasks—like routing, performance optimizations, code bundling, and more—so you don’t have to stitch them together from scratch.

With Next.js, you get features such as:

• Built-in Routing: File-system–based routing means you create pages by placing files in a specific folder structure, no extra libraries needed.

• Server-Side Rendering & Static Generation: Helps improve performance and SEO by rendering pages on the server or at build time.

• API Routes: Build your backend logic within the same Next.js project.

• Optimized Image and Font Handling: No need for separate libraries to optimize images.

• Server and Client Components: A new approach where you can decide which parts of your UI render on the server and which parts render on the client for maximum performance.

  
  

If you’re new to React and you already know you want a robust, scalable solution, you can jump straight into Next.js without having to manually configure React.

4. Understanding the Browser and the DOM

When a user visits a website, the browser requests an HTML file from a server. This HTML is then turned into a Document Object Model (DOM)—a tree-like representation of all elements on the page. You can manipulate the DOM using JavaScript, such as document.getElementById or document.createElement, to dynamically update the UI.

While this imperative approach works for small tasks, it can become verbose and error-prone for large applications. React’s declarative style lets you describe what the UI should look like, and React figures out how to update the DOM for you.

5. Going from Imperative to Declarative

Imperative code spells out how to do something—like step-by-step instructions for the browser to create or remove elements.Declarative code focuses on what the result should be—like telling React, “Render a list of blog posts,” without specifying exactly how to manipulate each DOM node.

JSX (the HTML-like syntax in React) is a big part of this declarative approach. You simply write what elements should appear, and React handles the underlying DOM changes.

6. Components, Props, and State in React

Three fundamental React concepts you need to know are:

1. Components

   A component is a function that returns UI. You nest and combine components to form complex interfaces. For example, a Header component might house your site’s logo and navigation links. A HomePage component could be composed of multiple smaller components like Header, Footer, and so on.

2. Props

   Props are like arguments to a JavaScript function. They let you pass data into a component so that the component can render it. For example:

function Header({ title }) {

  return <h1>{title}</h1>;

}

function HomePage() {

  return (

    <div>

      <Header title="Welcome to My Blog" />

    </div>

  );

}

Here, "Welcome to My Blog" is passed as the title prop.

3. State

   State is used for data that changes over time, especially due to user interaction. For instance, a “Like” button might track the number of times it’s been clicked. You can store this with the useState hook:

import { useState } from 'react';

function LikeButton() {

  const [likes, setLikes] = useState(0);

  function handleClick() {

    setLikes(likes + 1);

  }

  return (

    <button onClick={handleClick}>

      Like ({likes})

    </button>

  );

}

Each time a user clicks “Like,” React updates the state, then re-renders the component with the new likes value.

7. Moving from React to Next.js

If you build a React app from scratch, you often have to configure bundling, routing, code splitting, optimization, and more. Next.js automates a lot of that:

1. Installation

   Ensure you have Node.js 18.17.0 or above. Then, create a package.json and install your dependencies:

   
   

npm install react react-dom next

2. File Structure and Pages

   In Next.js, you can create an app folder (or pages folder in older versions) and place your main page in app/page.js. This file becomes your homepage route. For example:

   
   

// app/page.js

export default function HomePage() { 
	return <h1>Hello from Next.js!</h1>; 
}

3. Server vs. Client Components

   By default, Next.js treats components as Server Components for better performance. If you want to use React features like useState or add interactive event handlers, you mark your file with 'use client' at the top to indicate it should run in the browser:

   
   

// app/like-button.js 

'use client'; 
import { useState } from 'react'; 

export default function LikeButton() { 
	const [likes, setLikes] = useState(0);
 	return ( 
		<button onClick={() => setLikes(likes + 1)}> 
		Like ({likes}) 
		</button> 
	);
 }

Then you can import LikeButton into your page:

// app/page.js 

import LikeButton from './like-button'; 

export default function HomePage() { 
	return ( 
		<div> 
			<h1>My Next.js App</h1> 
			<LikeButton /> 
		</div> 
	);
}

3. Development Server

   Add a script to your package.json for development:

   
   

{ 
	"scripts": { 
		"dev": "next dev" 
	}, 

	"dependencies": { 
		"next": "latest",
		"react": "latest",
 		"react-dom": "latest" 
	} 
}

Then run:

npm run dev

Navigate to http://localhost:3000 to see your Next.js application.

8. Server and Client Components in Action

Next.js’ Server Components fetch data or generate HTML on the server, sending only the minimal data needed to the client. This can significantly speed up load times. Client Components, by contrast, let you handle user interactions, manage UI state, and respond to events in the browser.

A common strategy is to keep most of your UI as Server Components (for performance) and only opt into Client Components where you need user interactivity (like forms, buttons, or dynamic content).

9. Where to Go Next

Once you’ve gotten comfortable writing React Components with props and state, and you’ve tried Next.js’ file-based routing and server/client components, you’ll see just how much Next.js automates for you.

There are many more Next.js features to explore:

• API Routes: Build APIs within the same project.

• Middleware: Run code before rendering pages for tasks like authentication or redirects.

• Image Optimization: Serve scaled and optimized images out of the box.

• Incremental Static Regeneration: Combine static site generation with dynamic updates, so you can rebuild pages incrementally.

  
  

Conclusion

React is your foundation for building interactive user interfaces, but frameworks like Next.js take those core ideas and scale them up for modern, production-ready applications. By handling routing, server-side rendering, bundling, and more, Next.js frees you up to focus on crafting a delightful user experience.

Whether you’re improving an existing site or starting from scratch, learning React and Next.js together is a powerful way to build fast, maintainable, and production-grade applications. Now that you understand the fundamentals, the best way forward is to start coding: pick a small project and begin putting these concepts into practice. Good luck, and happy coding!