The Evolution of Rendering in React: From Client-Side to Server Components

 

🚀 The Evolution of Rendering in React: From Client-Side to Server Components

React has evolved massively in how it renders pages, moving from Client-Side Rendering (CSR) to Server Components (RSC) to improve performance, SEO, and user experience.

Let's break this down step by step:

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🔥 1️⃣ Client-Side Rendering (CSR) – The Beginning

📌 What is CSR?

• In Client-Side Rendering (CSR), the browser downloads a bare HTML file and a JavaScript bundle.
• React runs entirely in the browser, generating the UI dynamically.

📌 How it Works?

1. Browser downloads an empty HTML file.
2. Loads a large JavaScript bundle containing React code.
3. React renders components dynamically and updates the DOM.

📌 Example: CSR in React (Create React App)

function App() {
  return <h1>Hello, world!</h1>;
}

export default App;

• The entire app loads and renders in the browser.
• No content is present in the initial HTML file.

📌 Challenges of CSR:
❌ Slow First Page Load – A blank page is shown until JavaScript loads.
❌ Bad for SEO – Search engines see an empty HTML file.
❌ Not optimized for performance – Large JavaScript bundles make apps slow.

📌 How to Fix? → Server-Side Rendering (SSR) & Static Site Generation (SSG)

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⚡ 2️⃣ Server-Side Rendering (SSR) & Static Site Generation (SSG)

To fix CSR’s slow loading times & SEO issues, React introduced Server-Side Rendering (SSR) & Static Site Generation (SSG).

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⚡ Server-Side Rendering (SSR)

📌 What is SSR?

• In Server-Side Rendering (SSR), the server renders React components into HTML before sending them to the browser.
• The user sees the content immediately without waiting for JavaScript to load.

📌 How it Works?

1. Browser requests a page → The server renders the React components into HTML.
2. HTML is sent to the browser, so users see content immediately.
3. JavaScript hydrates the page to add interactivity.

📌 Example: Next.js SSR

export async function getServerSideProps() {
  const res = await fetch("https://jsonplaceholder.typicode.com/posts/1");
  const data = await res.json();
  return { props: { data } };
}

export default function Page({ data }) {
  return <h1>{data.title}</h1>;
}

• The server fetches data and generates HTML before sending it to the browser.

📌 Challenges of SSR:
❌ Server Load – Rendering every request on the server can be slow.
❌ Latency – Users wait for the server to respond before seeing anything.

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📌 Static Site Generation (SSG) – Faster Alternative to SSR

📌 What is SSG?

• Pre-renders pages at build time instead of on every request.
• The HTML is cached and served instantly, making it super fast.

📌 How it Works?

1. Pages are generated at build time (not on every request).
2. Static HTML is stored on a CDN for instant loading.

📌 Example: Next.js SSG

export async function getStaticProps() {
  const res = await fetch("https://jsonplaceholder.typicode.com/posts/1");
  const data = await res.json();
  return { props: { data } };
}

export default function Page({ data }) {
  return <h1>{data.title}</h1>;
}

✔ Faster than SSR because HTML is pre-generated.
✔ Great for SEO and performance.

📌 Challenges of SSG:
❌ Not real-time – The page is static until the next deployment.
❌ Not dynamic – You need revalidation or API calls for fresh data.

📌 How to Fix? → Suspense for SSR

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🚀 3️⃣ Suspense for Server-Side Rendering (SSR) – Faster Streaming

📌 What is Suspense SSR?

• Allows progressive streaming – sends HTML as soon as it’s ready instead of waiting for everything.
• Uses React Suspense to show loading states only where needed.

📌 How it Works?

1. The server streams HTML chunks to the browser.
2. Skeleton UI appears first, and then the data loads dynamically.

📌 Example: Streaming SSR with Suspense

import { Suspense } from "react";

function Page() {
  return (
    <div>
      <h1>My Page</h1>
      <Suspense fallback={<p>Loading...</p>}>
        <UserProfile />
      </Suspense>
    </div>
  );
}

✔ Faster page load times.
✔ Improves perceived performance.

📌 Challenges of Suspense SSR:
❌ Still requires client-side JavaScript for interactivity.

📌 How to Fix? → Server Components (RSC)

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🎉 4️⃣ Server Components (RSC) – The Best of Both Worlds

📌 What are Server Components?

• React can now run components directly on the server, removing unnecessary client-side JavaScript.
• No need to hydrate everything – only interactive parts need JavaScript.

📌 How it Works?

1. The server renders UI components, including database calls.
2. The browser receives only minimal JavaScript (only for interactive parts).

📌 Example: Server Component (.server.js)

// Runs ONLY on the server
export default async function ServerComponent() {
  const res = await fetch("https://jsonplaceholder.typicode.com/posts/1");
  const data = await res.json();
  return <h1>{data.title}</h1>;
}

✔ No client-side JavaScript needed – everything is processed on the server.
✔ Smaller bundles → Faster loading pages.

📌 Challenges of Server Components:
❌ No access to useState, useEffect (since it runs on the server).
❌ Need client components for interactivity.

📌 Solution? → Mix Server & Client Components!

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🔄 5️⃣ Mixing Server & Client Components (Best Practice)

📌 Why use both?

• Server Components for fast, efficient rendering & data fetching.
• Client Components for interactivity like buttons & forms.

📌 Example: Mixing Both

// Server Component
import ClientComponent from "./ClientComponent";

export default async function ServerComponent() {
  const res = await fetch("https://jsonplaceholder.typicode.com/posts/1");
  const data = await res.json();

  return (
    <div>
      <h1>{data.title}</h1>
      <ClientComponent />
    </div>
  );
}

// Client Component
"use client";
import { useState } from "react";

export default function ClientComponent() {
  const [count, setCount] = useState(0);

  return <button onClick={() => setCount(count + 1)}>Clicked {count} times</button>;
}

✔ Server Component fetches data efficiently.
✔ Client Component handles interactivity.

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🎯 Final Summary: Evolution of React Rendering

Rendering Method	Pros	Cons
Client-Side Rendering (CSR)	Interactive, dynamic	Slow first load, bad for SEO
Server-Side Rendering (SSR)	Better SEO, no blank screens	Slower than SSG, server load
Static Site Generation (SSG)	Fastest, CDN caching	Not real-time
Suspense SSR	Faster streaming	Still needs client-side JavaScript
Server Components (RSC)	No client JavaScript needed	No useState, useEffect

🚀 By mixing Server & Client Components, we get the best performance!