Million.js Has a Free React Compiler — Here's How to Use It

#javascript #react #performance #optimization

React re-renders entire component trees when state changes. Virtual DOM diffing is fast but not free. Million.js replaces React's Virtual DOM with direct DOM manipulation — up to 70% faster.

What Is Million.js?

Million.js is a drop-in compiler that optimizes React components. It analyzes your components at build time and replaces Virtual DOM operations with direct DOM updates.

Quick Start

npm install million

// vite.config.ts
import million from 'million/compiler';
import react from '@vitejs/plugin-react';

export default {
  plugins: [
    million.vite({ auto: true }), // Auto-optimize all components
    react(),
  ],
};

That's it. Your existing React app is now faster. No code changes needed.

How It Works

// Your code stays the same
function Counter() {
  const [count, setCount] = useState(0);

  return (
    <div>
      <p>Count: {count}</p>
      <button onClick={() => setCount(count + 1)}>+1</button>
    </div>
  );
}

// Million.js compiler transforms it at build time:
// Instead of: Full VDOM diff → find changes → patch DOM
// Million does: Direct DOM update → element.textContent = count

Performance Gains

Scenario	React	React + Million.js
List re-render (1K items)	45ms	12ms
State update	8ms	2ms
Initial render	Same	Same
Bundle overhead	0	+3KB

Manual Optimization

For fine-grained control:

import { block } from 'million/react';

const UserCard = block(function UserCard({ name, email, avatar }) {
  return (
    <div className="card">
      <img src={avatar} alt={name} />
      <h2>{name}</h2>
      <p>{email}</p>
    </div>
  );
});

When Million.js Helps Most

Data-heavy UIs — dashboards, tables, lists
Frequent re-renders — real-time data, animations
Large component trees — complex page layouts
Low-end devices — mobile browsers, older hardware

Limitations

Million.js works best with:

Pure components (no side effects in render)
Static structure (conditional rendering may not optimize)
Primitive props (objects/arrays work but less optimal)

Framework Support

Vite — million.vite()
Next.js — million.next()
webpack — million.webpack()
Rollup — million.rollup()

Get Started

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