React 19 and Server Actions: What You Must Master in 2026

// Example of Server Actions with useActionState in React 19
'use client';
import { useActionState } from 'react';

async function updateProfile(prevState: any, formData: FormData) {
  const username = formData.get('username') as string;
  // Server-side database operation
  return { message: `Profile updated for ${username}`, success: true };
}

export function ProfileForm() {
  const [state, formAction, isPending] = useActionState(updateProfile, null);

  return (
    <form action={formAction} className="space-y-4">
      <input name="username" placeholder="Your name" required />
      <button type="submit" disabled={isPending}>
        {isPending ? 'Saving...' : 'Update'}
      </button>
      {state?.message && <p>{state.message}</p>}
    </form>
  );
}