React 18 Alpha: Automatic Batching

React 18 (in alpha at this time) introduces **Automatic Batching**. Previously, React only batched state updates inside event handlers. Now it batches everywhere—setTimeout, Promises, native events.

Before React 18

// Two re-renders!
setTimeout(() => {
  setCount(c => c + 1);
  setFlag(f => !f);
}, 1000);

After React 18

// One re-render (batched!)
setTimeout(() => {
  setCount(c => c + 1);
  setFlag(f => !f);
}, 1000);

Key Takeaways

• Use `flushSync` if you explicitly need an immediate render.
• This reduces rendering overhead significantly in complex apps.