React

React Protocol

Component Structure

• Functional components only (no classes)
• No import React from 'react' — import individually
• Never use React.* namespace (e.g., React.useState, React.ReactNode)
• Export default in single expression
• No return types for components (TypeScript infers)

// ✓ Good
import { useState, type ReactNode } from 'react';

export default function MyComponent() {
  return <div>Hello</div>;
}

// ✗ Bad
import React from 'react';
function MyComponent(): JSX.Element { ... }
export default MyComponent;

Hooks

• useState generic only for unions/complex types (not for string, boolean, number)
• No useCallback for same-component functions
• useCallback acceptable for functions returned from custom hooks
• Named functions (not arrows) for async/complex logic inside hooks

// ✓ Good
const [name, setName] = useState(''); // no generic needed
const [status, setStatus] = useState<'a' | 'b'>('a'); // union needs generic

useEffect(() => {
  async function fetchData() {
    const res = await fetch('/api');
  }
  void fetchData();
}, []);

Other Rules

• Follow accessibility best practices
• displayName only for forwardRef components
• Fragment <> only for multiple siblings

// ✓ forwardRef with displayName
const MyInput = forwardRef<HTMLInputElement, Props>((props, ref) => (
  <input ref={ref} {...props} />
));
MyInput.displayName = 'MyInput';

// ✓ Fragment for siblings
return (
  <>
    <div>First</div>
    <div>Second</div>
  </>
);

// ✗ Unnecessary fragment
return (
  <>
    <div>Only child</div>
  </>
);