React Components

Requirement A component MUST be a function component using hooks, not a class component.

Rationale Hooks are the reactivity model the renderer understands. Class lifecycle methods fall out of every component. An effect covers what derivation cannot express.

Example

function OrderTotal({ orderId }: { orderId: string }) {
  const [quantity, setQuantity] = useState(1);
  const unitPrice = useUnitPrice(orderId);
  const total = quantity * unitPrice;
  return <Price value={total} />;
}

Requirement A component MUST type its props and its events under strict mode.

Rationale An untyped prop fails at the call site the next author writes, which is the most expensive place to learn a shape. Strict mode turns that failure into a build error.