⚛️ React 18+ in Action: What’s New and How to Migrate from Older Versions

React continues to evolve — and with React 18 and above, it introduced several game-changing features that improve performance, user experience, and developer flexibility.

In this article, we’ll cover:

• 🔍 What’s new in React 18+

• ⚙️ How to upgrade from older versions

• 🧩 Common issues & how to fix them

• ✅ Real-world tips for smooth migration

🚀 What’s New in React 18+

React 18 introduced Concurrent Rendering, automatic batching, and a new root API, among other features. Here’s a quick breakdown:

🔄 Concurrent Rendering

Lets React interrupt rendering to prioritize more urgent updates, improving UX and responsiveness.

import { createRoot } from 'react-dom/client';

const root = createRoot(document.getElementById('root'));

root.render();

🔧 Note: This replaces ReactDOM.render().

📦 Automatic Batching

React now batches more updates together, improving performance.

// Before: Would cause 2 renders

setCount(c => c + 1); setFlag(f => !f);

// Now in React 18+: 1 render thanks to automatic batching

🧵 startTransition()

For UI updates that don’t need to block user interaction.

import { startTransition } from 'react';

startTransition(() => {

setValue(inputValue);

});

🧪 useId() Hook

Generates unique IDs on the client & server — super helpful in SSR or accessibility.

const id = useId();

<label htmlFor={id}>Name</label>

<input id ={id}/>

📈 Why Upgrade?

• ⚡ Improved rendering speed

• 🔄 Better user interactions

• 🤝 Prepares you for future React features

• 🧠 Cleaner, more modern APIs

🔄 How to Upgrade (Step-by-Step)

1️⃣ Install React 18

npm install react@latest react-dom@latest

2️⃣ Replace ReactDOM.render()

Before:ReactDOM.render(, document.getElementById('root'));

After:

import { createRoot } from 'react-dom/client';

const root = createRoot(document.getElementById('root'));

root.render();

3️⃣ Watch for Deprecated Features

Check your console warnings and update any legacy APIs (e.g., componentWillMount).

🛠️ Common Issues & Solutions

📌 Final Thoughts

React 18+ is all about smoother, smarter rendering. If you’re still using an older version, now is the time to upgrade — and you don’t have to rewrite your app to do it.

Code Reacher will continue to bring you migration guides, tutorials, and deep dives into the tech that’s shaping our future.

🔗 References

• React 18 Release Notes

• Upgrading to React 18

• React Docs