React Server Components Guide: Boost Performance and Reduce Bundle Size ✨🚀
Tags: react, nextjs, webdev, frontend
Published: 2023-10-31 10:58:49

Hello there 👋 I'm excited to share with you today an in-depth exploration of **React Server Components**, a new feature that's been making waves in the React ecosystem. This feature is part of the latest **Next.js 14** release, and we'll dive into how you can leverage it to optimize your applications' **performance**.

So, prepare yourself for an enlightening exploration of the fascinating realm of React Server Components! 🎉

## What Are React Server Components?

React Server Components, or **RSCs**, for short, are a groundbreaking addition to **React**, aimed at enabling components to render on the server side. The crux of RSCs lies in their ability to fetch data at the source, i.e., the server, thereby nullifying the need to ship unnecessary JavaScript to the client.

The result? Lightning-fast initial page loads and a drastic reduction in bundle size. But that's not all! With RSCs, your sensitive data and logic stay securely on the server, safeguarding them from exposure to the client side.

However, it's important to remember that RSCs are devoid of the client-side interactivity that traditional React components offer. Hence, certain React hooks and APIs are off-limits with RSCs.

## The Evolution of Server Components in Next.js 14

With the advent of Next.js 14, React Server Components have found a new playground. A major shift that Next.js 14 brings to the table is the introduction of the **App Router**, which sits alongside the existing Pages Router.

Interestingly, any component nestled within the App Router is, **by default**, considered a Server Component. These Server Components are rendered on the server and delivered to the client as static HTML.

It's also worth noting that Next.js 14 has bid adieu to the traditional `getStaticProps` and `getServerSideProps` methods for data fetching and instead introduced a new native fetch API. This API works like a charm with both Server and Client Components, supporting features like caching and incremental static regeneration.

## The Art and Science of Pre-rendering in Next.js

Pre-rendering in Next.js is an art that's mastered with a blend of two techniques - **SSR** and **SSG**. Both these techniques have their strengths and weaknesses but together, they offer a formidable approach to pre-rendering.

SSR involves fetching data on the server, generating HTML pages per route, and delivering these to the client's browser. The browser then hydrates these HTML pages into a dynamic React application.

On the other hand, SSG takes a proactive approach and generates HTML pages at build time, reducing the load on the browser and providing a better user experience.

However, as powerful as these techniques are, they come with their fair share of challenges. SSR can be resource-intensive, while SSG can extend build times for large applications.

This is where React Server Components come into play, offering a new perspective on pre-rendering and addressing the challenges posed by SSR and SSG.

## Unleashing the Potential of React Server Components

RSCs work in harmony with both SSR and SSG to pre-render individual components on the server. This results in enhanced performance, reduced client-side JavaScript, and shorter build times.

Let's delve into how we can implement RSCs to supercharge our Next.js applications. 🚀

```jsx
const ServerComponent = () => {
  const data = "I'm a Server Component.";

  console.log(data);

  return <p>{data}</p>;
};

export default ServerComponent;

```

In the code snippet above, we create a simple React Server Component. It logs a message and returns a paragraph element with the same message. Let's imagine that console.log is a complex function with a lot of code that could potentially impact our bundle size and execution time. It might sound concerning if it were true, but it's just a thought experiment. So, what advantage do we gain by keeping this code inside a Server Component? The result sent to the browser is merely an **HTML markup** without any JavaScript code. The code execution only occurs on the server-side, saving our page from unnecessary code and performance issues. ⚡️

## Leveraging React Suspense for Fallbacks

With Suspense, React 18 introduces support for data fetching. This allows you to display a fallback component while another component is loading its data. This can be particularly useful for displaying loading spinners or placeholders while a component is fetching data from the server. 💫

```jsx
const Index = async () => {
  return (
    <>
      <Suspense fallback={<h2>Loading...</h2>}>
        {/* A component that's fetching data to display cards */}
        <BlogPosts />
      </Suspense>
    </>
  );
};

```

In the above example, while the `BlogPosts` component is fetching data, the `Suspense` component renders a fallback component with the text "Loading…". ⏳

## The Dance of Client Components and Server Components

In the world of Next.js 14, Client Components and Server Components exist harmoniously. Client Components are rendered on the client side, much like traditional React components. To mark a component as a Client Component, you need to use the 'use client' directive. 🕺💃

```jsx
"use client";

import { useState } from "react";

const ClientComponent = ({ ServerComponent }) => {
  const [count, setCount] = useState(0);

  return (
    <>
      <h3>Client Component</h3>
      <button onClick={() => setCount(count + 1)}>Increment</button>
      <p>Count: {count}</p>
            { count > 10 && <ServerComponent /> }
    </>
  );
};

export default ClientComponent;

```

In the provided code snippet, we have a Client Component that is responsible for rendering on the client side in Next.js 14. To designate a component as a Client Component, the "use client" directive is used.

The Client Component, named `ClientComponent`, is a functional component that utilizes the `useState` hook from React. It receives a `ServerComponent` as a prop.

Within the component, there is a state variable `count` and a button that increments the count when clicked. The current count is displayed in a paragraph element.

The interesting part is the conditional rendering of the `ServerComponent`. When the count exceeds 10, the `ServerComponent` is rendered. This condition is achieved by using a ternary operator (`{ count > 10 && <ServerComponent /> }`) within the JSX code.

It's important to note that Server Components cannot be directly imported into Client Components. However, they can be passed as props to Client Components and rendered conditionally based on certain criteria, as demonstrated in this code snippet.

Overall, the Client Component provides a dynamic and interactive user interface, allowing the rendering of the Server Component based on specific conditions. 🤝

## The Pros and Cons of React Server Components

While RSCs bring numerous advantages to the table, they're not without their drawbacks.

The benefits of RSCs include:

1. Improved performance: RSCs offer a significant performance boost by reducing the browser's workload.
2. Enhanced SEO: RSCs can enhance the SEO of your Next.js apps, leading to better search results.
3. Greater flexibility: RSCs provide more flexibility in how you render your Next.js applications.

However, the challenges include:

1. Complexity: Implementing RSCs can be more complex than traditional React components, requiring a steeper learning curve.
2. Limited compatibility: RSCs may not be compatible with all libraries and tools in the React ecosystem. ❗️

## Wrapping Up

The introduction of React Server Components is a game-changer in how we build React and Next.js applications. While it may seem overwhelming at first, as the RSC feature stabilizes, it's bound to contribute to an improved developer experience.

In the meantime, feel free to stick to traditional app development methods if you're more comfortable with those. And remember, don't hesitate to experiment and learn something new!

I hope this guide helps you understand the ins and outs of React Server Components in Next.js 14. If you found it helpful, don't forget to give it a 👍 and share it with your fellow developers. For more such content, feel free to follow me on [Twitter](https://twitter.com/UsulPro).

Also, make sure to check out my article on another upcoming React feature: [How React Forget will make React useMemo and useCallback hooks absolutely redundant](https://dev.to/usulpro/how-react-forget-will-make-react-usememo-and-usecallback-hooks-absolutely-redundant-4l68). It's an insightful read that complements your understanding of React's evolving ecosystem.

Remember, the road to learning is never-ending. So, keep exploring, keep learning, and most importantly, keep coding! 🚀

🌟🌟🌟