skills/b4r7x/agent-skills/react-design-patterns

react-design-patterns

SKILL.md

React Design Patterns

Overview

13 patterns ranked by 2025 popularity. Golden rule: start with a Custom Hook — upgrade to Compound Components only if structural sharing is needed.

Pattern Decision Guide

Need Pattern
Reusable logic, no UI opinion Custom Hook
Controlled vs uncontrolled component behavior Control Props
Tightly coupled UI subcomponents (Tabs, Modal, Accordion) Compound Components
Logic without imposed styling Headless Component
Separate data fetching from rendering Container / Presentational
Global stable state (auth, theme) Provider (Context)
Reverse data flow (child → parent) Render Props
Full render control via children Children as Function
Flexible API with pre-built props Props Getters
Crash isolation Error Boundary
Render outside DOM parent (modals, tooltips) Portal
Design system hierarchy Atomic Design

1. Custom Hook ⭐⭐⭐⭐⭐

Extract stateful logic into a reusable function. Most popular pattern in 2025.

function useLocalStorage(key, initialValue) {
  const [value, setValue] = useState(() => {
    try { return JSON.parse(localStorage.getItem(key)) ?? initialValue; }
    catch { return initialValue; }
  });
  const set = useCallback((v) => {
    setValue(prev => {
      const next = v instanceof Function ? v(prev) : v;
      localStorage.setItem(key, JSON.stringify(next));
      return next;
    });
  }, [key]);
  return [value, set];
}

2. Control Props ⭐⭐⭐⭐

Component supports both controlled (parent owns state via props) and uncontrolled (manages own state) modes. Every form input and component library uses this.

// Controlled — parent manages state
<EditableTitle title={title} onChange={setTitle} />

// Uncontrolled — component manages own state, parent can reset via key
<EditableTitle key={userId} defaultTitle="Untitled" />

// Implementation supporting both modes
function EditableTitle({ title, defaultTitle = '', onChange }) {
  const [internal, setInternal] = useState(defaultTitle);
  const isControlled = title !== undefined;
  const value = isControlled ? title : internal;

  const handleChange = (e) => {
    if (!isControlled) setInternal(e.target.value);
    onChange?.(e.target.value);
  };

  return <input value={value} onChange={handleChange} />;
}

3. Compound Components ⭐⭐⭐⭐

Family of subcomponents sharing state via local context. Used by Radix UI, Headless UI, React Aria.

const TabsContext = createContext(null);
function Tabs({ children, defaultTab }) {
  const [activeTab, setActiveTab] = useState(defaultTab);
  const value = useMemo(() => ({ activeTab, setActiveTab }), [activeTab]);
  return <TabsContext.Provider value={value}>{children}</TabsContext.Provider>;
}
Tabs.Tab = function({ id, children }) {
  const { activeTab, setActiveTab } = useContext(TabsContext);
  return <button className={activeTab === id ? 'active' : ''} onClick={() => setActiveTab(id)}>{children}</button>;
};
Tabs.Panel = function({ id, children }) {
  const { activeTab } = useContext(TabsContext);
  return activeTab === id ? <div>{children}</div> : null;
};

Always guard with a custom hook:

function useTabs() {
  const ctx = useContext(TabsContext);
  if (!ctx) throw new Error('Tabs.* must be used inside <Tabs>');
  return ctx;
}

4. Headless Component ⭐⭐⭐⭐

Hook provides logic only — zero HTML, zero CSS. You own the UI completely.

function useAccordion() {
  const [openIndex, setOpenIndex] = useState(null);
  const toggle = useCallback((i) => setOpenIndex(prev => prev === i ? null : i), []);
  const isOpen = useCallback((i) => openIndex === i, [openIndex]);
  return { toggle, isOpen };
}
// Two completely different UIs can use the same hook

5. Container / Presentational ⭐⭐⭐

Split into: Container (logic, fetch, navigation) and Presentational (receives data via props, renders only).

// Presentational — pure UI, easy to test
const UserCard = ({ user, onFollow }) => (
  <div><h2>{user.name}</h2><button onClick={onFollow}>Follow</button></div>
);
// Container — logic and data
const UserCardContainer = ({ userId }) => {
  const { user, follow } = useUser(userId);
  if (!user) return <Skeleton />;
  return <UserCard user={user} onFollow={follow} />;
};

6. Provider (Context) ⭐⭐⭐⭐

createContext + useContext for global/local state. See react-usecontext skill for full details.

7. Render Props ⭐⭐

Pass a function as prop — component calls it with data:

<WindowSize render={({ width }) => (
  width < 768 ? <MobileMenu /> : <DesktopMenu />
)} />

Useful for reverse data flow (child → parent). Mostly replaced by custom hooks in 2025.

8. Children as Function ⭐⭐

Variant of render props — function passed as children. Popularized by Formik, Downshift:

<Toggle>
  {({ on, toggle }) => (
    <button onClick={toggle}>{on ? 'ON' : 'OFF'}</button>
  )}
</Toggle>

9. Props Getters ⭐⭐

Hook returns pre-built prop objects to spread on elements. Used by React Hook Form (register), react-table:

function useToggle() {
  const [on, setOn] = useState(false);
  const getTogglerProps = (overrides = {}) => ({
    onClick: () => setOn(prev => !prev),
    'aria-pressed': on,
    ...overrides,
  });
  return { on, getTogglerProps };
}
// Usage: <button {...getTogglerProps({ className: 'my-btn' })}>

10. Error Boundary ⭐⭐

Catches JS errors in the component tree, shows fallback UI. Requires class component or react-error-boundary library:

import { ErrorBoundary } from 'react-error-boundary';
<ErrorBoundary FallbackComponent={ErrorFallback} onReset={() => { /* reset state */ }}>
  <Dashboard />
</ErrorBoundary>

Underused — most apps should have granular error boundaries per section.

11. Portal ⭐⭐⭐

Renders outside the DOM parent tree. Solves z-index, overflow: hidden, clipping:

import { createPortal } from 'react-dom';
function Modal({ isOpen, children }) {
  if (!isOpen) return null;
  return createPortal(
    <div className="modal-overlay">{children}</div>,
    document.body
  );
}

12. HOC (Higher-Order Component) ⭐ — Legacy

Function that takes a component, returns a new component. Replaced by custom hooks in modern code.

// Legacy
const ProtectedDashboard = withAuth(Dashboard);
// Modern equivalent
function ProtectedRoute({ children }) {
  const { user } = useAuth();
  if (!user) return <Navigate to="/login" />;
  return children;
}

13. Atomic Design ⭐⭐⭐

Hierarchy: Atoms (Button) → Molecules (SearchBox = Input + Button) → Organisms (Header) → Templates (layout without data) → Pages (template with data). Great for design systems and large team projects.

References

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