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React State Management
Comprehensive guide to modern React state management patterns, from local component state to global stores and server state synchronization.
When to Use This Skill
- Setting up global state management in a React app
- Choosing between Redux Toolkit, Zustand, or Jotai
- Managing server state with React Query or SWR
- Implementing optimistic updates
- Debugging state-related issues
- Migrating from legacy Redux to modern patterns
Core Concepts
1. State Categories
| Type | Description | Solutions |
|---|---|---|
| Local State | Component-specific, UI state | useState, useReducer |
| Global State | Shared across components | Redux Toolkit, Zustand, Jotai |
| Server State | Remote data, caching | React Query, SWR, RTK Query |
| URL State | Route parameters, search | React Router, nuqs |
| Form State | Input values, validation | React Hook Form, Formik |
2. Selection Criteria
Small app, simple state → Zustand or Jotai
Large app, complex state → Redux Toolkit
Heavy server interaction → React Query + light client state
Atomic/granular updates → JotaiQuick Start
Zustand (Simplest)
typescript
// store/useStore.ts
import { create } from 'zustand'
import { devtools, persist } from 'zustand/middleware'
interface AppState {
user: User | null
theme: 'light' | 'dark'
setUser: (user: User | null) => void
toggleTheme: () => void
}
export const useStore = create<AppState>()(
devtools(
persist(
(set) => ({
user: null,
theme: 'light',
setUser: (user) => set({ user }),
toggleTheme: () => set((state) => ({
theme: state.theme === 'light' ? 'dark' : 'light'
})),
}),
{ name: 'app-storage' }
)
)
)
// Usage in component
function Header() {
const { user, theme, toggleTheme } = useStore()
return (
<header className={theme}>
{user?.name}
<button onClick={toggleTheme}>Toggle Theme</button>
</header>
)
}Detailed patterns and worked examples
Detailed pattern documentation lives in references/details.md. Read that file when the navigation tier above is insufficient.
Best Practices
Do's
- Colocate state - Keep state as close to where it's used as possible
- Use selectors - Prevent unnecessary re-renders with selective subscriptions
- Normalize data - Flatten nested structures for easier updates
- Type everything - Full TypeScript coverage prevents runtime errors
- Separate concerns - Server state (React Query) vs client state (Zustand)
Don'ts
- Don't over-globalize - Not everything needs to be in global state
- Don't duplicate server state - Let React Query manage it
- Don't mutate directly - Always use immutable updates
- Don't store derived data - Compute it instead
- Don't mix paradigms - Pick one primary solution per category
Migration Guides
From Legacy Redux to RTK
typescript
// Before (legacy Redux)
const ADD_TODO = "ADD_TODO";
const addTodo = (text) => ({ type: ADD_TODO, payload: text });
function todosReducer(state = [], action) {
switch (action.type) {
case ADD_TODO:
return [...state, { text: action.payload, completed: false }];
default:
return state;
}
}
// After (Redux Toolkit)
const todosSlice = createSlice({
name: "todos",
initialState: [],
reducers: {
addTodo: (state, action: PayloadAction<string>) => {
// Immer allows "mutations"
state.push({ text: action.payload, completed: false });
},
},
});