React 18: What’s New & Why You Should Upgrade

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📅 Published at: January 10, 2022

With the release of React 18, the React team introduced powerful new features aimed at improving performance and developer experience. This update focuses on automatic batching, concurrent rendering, and Suspense improvements, making React apps more efficient and responsive.

If you’re still using React 17, this guide will help you understand what’s new, why you should upgrade, and how to migrate your project smoothly.

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🔹 What’s New in React 18?

1. Automatic Batching for State Updates

Before React 18, multiple state updates inside event handlers could trigger multiple re-renders. With automatic batching, React now groups these updates into a single re-render, reducing performance overhead.

Example (Before React 18):

import { useState } from "react";

function Counter() {
  const [count, setCount] = useState(0);
  const [text, setText] = useState("");

  const handleClick = () => {
    setCount(count + 1);
    setText("Updated!"); // Triggers an extra re-render
  };

  return (
    <div>
      <p>Count: {count}</p>
      <p>{text}</p>
      <button onClick={handleClick}>Click Me</button>
    </div>
  );
}

➡️ Each state update triggers a separate re-render.

With React 18’s Automatic Batching:

import { useState } from "react";

function Counter() {
  const [count, setCount] = useState(0);
  const [text, setText] = useState("");

  const handleClick = () => {
    setCount(count + 1);
    setText("Updated!"); // Both updates are batched into a single re-render
  };

  return (
    <div>
      <p>Count: {count}</p>
      <p>{text}</p>
      <button onClick={handleClick}>Click Me</button>
    </div>
  );
}

✅ React batches these state updates together, resulting in fewer re-renders and better performance.

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2. Concurrent Rendering for Smoother UI Updates

Concurrent Rendering is a game-changer for improving UI responsiveness. It allows React to pause and resume rendering work, preventing laggy interfaces.

🔹 How does this help?

• Keeps UI responsive during heavy updates.
• Prevents unnecessary blocking of the main thread.
• Improves user experience in large apps.

New useTransition Hook (Example)

import { useState, useTransition } from "react";

function SearchList({ items }) {
  const [query, setQuery] = useState("");
  const [filteredItems, setFilteredItems] = useState(items);
  const [isPending, startTransition] = useTransition();

  const handleSearch = (e) => {
    setQuery(e.target.value);

    startTransition(() => {
      setFilteredItems(items.filter(item => item.includes(e.target.value)));
    });
  };

  return (
    <div>
      <input type="text" value={query} onChange={handleSearch} placeholder="Search..." />
      {isPending && <p>Loading...</p>}
      <ul>
        {filteredItems.map((item, index) => <li key={index}>{item}</li>)}
      </ul>
    </div>
  );
}

✅ startTransition() delays non-urgent state updates, keeping the UI smooth even with large lists.

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3. Suspense for Data Fetching (Improved!)

React Suspense is now better optimized for handling async data fetching. It simplifies working with async components and API calls.

Example of Using Suspense with Data Fetching

import { Suspense, lazy } from "react";

const UserProfile = lazy(() => import("./UserProfile"));

function App() {
  return (
    <Suspense fallback={<p>Loading...</p>}>
      <UserProfile />
    </Suspense>
  );
}

✅ Suspense ensures that the component only renders when data is ready, preventing flickering UIs.

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🛠️ How to Upgrade from React 17 to React 18

Step 1: Update Dependencies

In your project, run:

npm install react@18 react-dom@18

or for Yarn:

yarn add react@18 react-dom@18

Step 2: Update index.js or main.jsx

If you are using ReactDOM.render(), update it to createRoot():

Before (React 17)

import React from "react";
import ReactDOM from "react-dom";
import App from "./App";

ReactDOM.render(<App />, document.getElementById("root"));

After (React 18)

import React from "react";
import { createRoot } from "react-dom/client";
import App from "./App";

const root = createRoot(document.getElementById("root"));
root.render(<App />);

✅ This enables concurrent rendering automatically.

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📌 Should You Upgrade to React 18?

✅ Yes, if you want:
✔️ Better performance with automatic batching.
✔️ Smoother UI with concurrent rendering.
✔️ Cleaner async rendering with Suspense improvements.
✔️ More efficient state updates with useTransition.

🚀 React 18 is fully backward-compatible, so upgrading is simple for most apps.

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🔚 Conclusion

React 18 is an important update that makes React apps faster and more efficient. The improvements in automatic batching, concurrent rendering, and Suspense make upgrading worth it. Start migrating today to take full advantage of these features!

🔹 Have you upgraded to React 18? Let me know your thoughts in the comments! 🚀

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