React Writing Code

Quick reference for writing production-quality React code. Each section summarizes the key rules — reference files provide full examples and edge cases.

React 19 Patterns

Server-First Model

Components are server components by default in frameworks that support them. Use "use client" only when the component needs browser APIs, hooks, or event handlers.

// Server Component — no directive needed
async function DoctorList() {
  const doctors = await getDoctors();
  return <ul>{doctors.map((d) => <DoctorCard key={d.id} doctor={d} />)}</ul>;
}