Feature	Description	Guide
Hooks	useState, useEffect, custom hooks	HOOKS.md
TypeScript	Props, state, event typing	TYPESCRIPT.md
State	Zustand, Context, useReducer	STATE.md
Forms	React Hook Form, Zod validation	FORMS.md
Testing	Vitest, Testing Library	TESTING.md
Performance	memo, useMemo, useCallback, Suspense	PERFORMANCE.md

Common Patterns

Typed Component with Props

interface UserCardProps {
  user: { id: string; name: string; email: string };
  onEdit: (user: UserCardProps['user']) => void;
  onDelete: (id: string) => void;
}

function UserCard({ user, onEdit, onDelete }: UserCardProps) {
  return (
    <div className="user-card">
      <h3>{user.name}</h3>
      <p>{user.email}</p>
      <button onClick={() => onEdit(user)}>Edit</button>
      <button onClick={() => onDelete(user.id)}>Delete</button>
    </div>
  );
}

Custom Hook for Data Fetching

function useFetch<T>(url: string) {
  const [data, setData] = useState<T | null>(null);
  const [loading, setLoading] = useState(true);
  const [error, setError] = useState<Error | null>(null);

  useEffect(() => {
    let cancelled = false;

    async function fetchData() {
      try {
        const res = await fetch(url);
        const json = await res.json();
        if (!cancelled) setData(json);
      } catch (e) {
        if (!cancelled) setError(e as Error);
      } finally {
        if (!cancelled) setLoading(false);
      }
    }

    fetchData();
    return () => { cancelled = true; };
  }, [url]);

  return { data, loading, error };
}

Form with Validation

import { useForm } from 'react-hook-form';
import { zodResolver } from '@hookform/resolvers/zod';
import { z } from 'zod';

const schema = z.object({
  email: z.string().email(),
  password: z.string().min(8),
});

function LoginForm() {
  const { register, handleSubmit, formState: { errors } } = useForm({
    resolver: zodResolver(schema),
  });

  const onSubmit = (data: z.infer<typeof schema>) => {
    console.log(data);
  };

  return (
    <form onSubmit={handleSubmit(onSubmit)}>
      <input {...register('email')} />
      {errors.email && <span>{errors.email.message}</span>}
      <input {...register('password')} type="password" />
      {errors.password && <span>{errors.password.message}</span>}
      <button type="submit">Login</button>
    </form>
  );
}

Workflows

Component Development

Define props interface with TypeScript
Create component with hooks
Extract reusable logic to custom hooks
Add error boundaries for fault isolation
Write tests with Testing Library

State Management Decision

Local state only       -> useState
Complex local state    -> useReducer
Shared across tree     -> Context + useReducer
App-wide state         -> Zustand/Redux
Server state           -> TanStack Query

Best Practices

Do	Avoid
Use functional components	Class components
Extract custom hooks	Duplicating effect logic
Memoize expensive computations	Premature optimization
Handle loading/error states	Assuming success
Use keys for lists	Index as key for dynamic lists

Project Structure

src/
├── App.tsx
├── main.tsx
├── components/         # Reusable UI components
├── hooks/              # Custom hooks
├── pages/              # Route components
├── stores/             # State management
├── services/           # API calls
├── utils/              # Helper functions
└── types/              # TypeScript types

For detailed examples and patterns, see reference files above.

building-react-apps

React

Quick Start

Features