React 치트시트

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검색하고 인쇄할 수 있는 React 19 참조 자료——컴포넌트, JSX, 훅, 새로운 Actions API, 컨텍스트, ref, 성능. 무료.

Components & JSX

function App() { return <h1>Hi</h1>; }

A function component returning JSX

export default function App() {}

Default-export a component

<Greeting name="Ada" />

Render a component with props

{1 + 2} or {user.name}

Embed a JS expression with braces

<>{a}{b}</>

Fragment groups nodes, no extra DOM

<div className="card">

Use className, not class, for CSS

{isOpen && <Menu />}

Render conditionally with &&

{ok ? <Yes /> : <No />}

Choose between nodes with a ternary

{items.map(i => <li key={i.id}>{i.t}</li>)}

Render a list from an array

function Btn({ label, onClick }) {}

Destructure props in the signature

function Card({ children }) { return children; }

Read nested JSX via the children prop

<input value={v} onChange={onChange} />

Controlled input bound to state

Rendering & setup

import { createRoot } from 'react-dom/client'

Import the client root API

createRoot(document.getElementById('root')).render(<App/>)

Mount the app into the DOM

import { StrictMode } from 'react'

Import StrictMode wrapper

<StrictMode><App /></StrictMode>

Surface bugs in development

import { hydrateRoot } from 'react-dom/client'

Import the hydration API

hydrateRoot(el, <App />)

Attach React to server HTML

root.unmount()

Tear down a mounted root

import App from './App.jsx'

Import a component from a module

<App {...props} />

Spread an object as props

export { Button, Card }

Named-export multiple components

State & effects

const [count, setCount] = useState(0)

Declare a state variable

setCount(c => c + 1)

Update from the previous value

setUser(u => ({ ...u, name }))

Update object state immutably

useEffect(() => { run(); }, [dep])

Run an effect when deps change

useEffect(() => { /* once */ }, [])

Run an effect only on mount

useEffect(() => () => cleanup(), [])

Return a cleanup function

const ref = useRef(null)

Hold a mutable value across renders

const [state, dispatch] = useReducer(r, init)

Manage complex state with a reducer

const theme = useContext(ThemeContext)

Read the nearest context value

const memo = useMemo(() => calc(a), [a])

Memoize an expensive computation

useLayoutEffect(() => {}, [])

Run synchronously after layout

useSyncExternalStore(sub, get)

Subscribe to an external store

React 19 hooks & APIs

import { use } from 'react'

Import the new use API

const data = use(promise)

Read a promise, suspends until ready

const theme = use(ThemeContext)

Read context, allowed conditionally

const [state, action, pending] = useActionState(fn, init)

Track state, action and pending

const [opt, addOpt] = useOptimistic(state, reducer)

Show an optimistic value instantly

const { pending } = useFormStatus()

Read the parent form submit status

const [isPending, startTransition] = useTransition()

Mark updates as non-urgent

startTransition(async () => await save())

Run an async Action in a transition

const deferred = useDeferredValue(value)

Defer a value to keep UI responsive

const id = useId()

Generate a stable unique id

<title>Page title</title>

Render metadata anywhere in the tree

function Input({ ref }) {}

ref is a normal prop, no forwardRef

Forms & Actions

<form action={handleSubmit}>

Pass a function as a form Action

function handleSubmit(formData) {}

Action receives the FormData

formData.get('email')

Read a field from FormData

const [state, action] = useActionState(submit, null)

Wire an Action to component state

<form action={action}>

Use the wrapped Action on the form

const [s, a, pending] = useActionState(fn, init)

Expose a pending flag for the UI

return { error: 'Invalid' }

Return error state from an Action

function Submit() { const { pending } = useFormStatus() }

Read pending inside the submit button

<button disabled={pending}>Save</button>

Disable submit while pending

import { requestFormReset } from 'react-dom'

Import the form reset helper

requestFormReset(formEl)

Reset an uncontrolled form

<form action={action}><Submit /></form>

Compose Action form with status

Props & composition

function Hi({ name = 'Guest' }) {}

Default prop via destructuring

function Box({ children }) { return children; }

Wrap content with the children prop

<Box><p>Inside</p></Box>

Pass JSX as children

function List({ render }) { return render(); }

Render prop pattern

<List render={() => <Item />} />

Provide a render function

<Input {...props} />

Forward all props with spread

const { id, ...rest } = props

Pick a prop and pass the rest

<Avatar {...rest} size="lg" />

Spread then override a prop

function Btn(props: BtnProps) {}

Type props with TypeScript interfaces

<Slot label={<b>Hi</b>} />

Pass JSX through a named prop

Events

<button onClick={handleClick}>

Attach a click handler

function handleClick(e) {}

Receive the synthetic event

<input onChange={e => set(e.target.value)} />

Read an input value on change

<form onSubmit={e => e.preventDefault()}>

Stop the default form submit

e.stopPropagation()

Prevent the event from bubbling

<li onClick={() => remove(id)}>

Pass arguments with a closure

<input onKeyDown={e => e.key === 'Enter'}

Handle a specific key press

<div onMouseEnter={hover}>

Listen for pointer events

e.currentTarget.value

Read the element the handler is on

<button onClick={() => {}} type="button">

Avoid implicit form submission

Lists & keys

arr.map(x => <li key={x.id}>{x.t}</li>)

Render one node per item

key={item.id}

Give each item a stable key

key={index}

Index keys only for static lists

users.map(u => <Card key={u.id} {...u} />)

Spread item fields as props

{list.length === 0 && <Empty />}

Show a fallback for empty lists

import { Fragment } from 'react'

Import Fragment for keyed groups

<Fragment key={id}>{a}{b}</Fragment>

A keyed fragment in a list

{rows.filter(r => r.on).map(...)}

Filter before mapping

Keys must be unique among siblings

Why keys help React diff lists

{[...Array(n)].map((_, i) => ...)}

Map a fixed-length range

Context

const ThemeContext = createContext('light')

Create a context with a default

import { createContext } from 'react'

Import the context factory

<ThemeContext value={theme}>

Provide a value (React 19 syntax)

<ThemeContext value={theme}><App /></ThemeContext>

Wrap the tree that reads it

const theme = useContext(ThemeContext)

Read context with useContext

const theme = use(ThemeContext)

Read context with the use API

if (cond) { const t = use(Ctx); }

use can read context conditionally

export const ThemeContext = createContext()

Export a shared context

<Ctx value={{ user, setUser }}>

Pass an object as the value

Avoid new objects each render

Memoize values to limit re-renders

Refs

const inputRef = useRef(null)

Create a ref holder

<input ref={inputRef} />

Attach the ref to a node

inputRef.current.focus()

Access the DOM node via current

function Field({ ref }) { return <input ref={ref} /> }

ref as a prop, no forwardRef

<Field ref={inputRef} />

Pass a ref to a component

useImperativeHandle(ref, () => ({ focus }))

Expose an imperative API

const setRef = node => { box = node; }

Use a callback ref

<div ref={setRef} />

Attach a callback ref

const count = useRef(0)

Store a value without re-rendering

ref={node => { return () => cleanup(); }}

Callback ref with cleanup (React 19)

Performance

const Memo = memo(Component)

Skip re-render when props are equal

import { memo } from 'react'

Import the memo helper

const value = useMemo(() => calc(a), [a])

Cache a computed value

const fn = useCallback(() => f(a), [a])

Cache a function identity

const Lazy = lazy(() => import('./Big.jsx'))

Code-split a component

import { lazy, Suspense } from 'react'

Import lazy and Suspense

<Suspense fallback={<Spin />}><Lazy /></Suspense>

Show a fallback while loading

startTransition(() => setQuery(q))

Mark non-urgent state updates

const slow = useDeferredValue(query)

Defer expensive derived UI

React Compiler auto-memoizes

Often removes manual memoization

Misc & metadata

<Suspense fallback={<Loading />}>

Boundary for async content

class ErrorBoundary extends Component {}

Catch render errors (legacy class)

<title>My Page</title>

Hoist document title from a component

<meta name="description" content="..." />

Render meta tags into the head

<link rel="stylesheet" href="..." />

Hoist a stylesheet link

<Comp key={id} />

Change key to remount a component

React.lazy(() => import('./Page.jsx'))

Lazily import a route component

createPortal(node, container)

Render into a different DOM node

{/* a comment */}

Write a comment inside JSX

cleanup return in useEffect

Always release subscriptions/timers

“:q”와 일치하는 항목이 없습니다.

React 치트시트 소개

이 React 치트시트는 React 19를 기준으로 개념별로 라이브러리를 정리했습니다: 컴포넌트와 JSX, 렌더링과 설정, 상태와 이펙트, React 19 훅과 API, 폼과 Actions, props와 컴포지션, 이벤트, 리스트와 키, 컨텍스트, ref, 성능, 그리고 메타데이터 및 기타입니다.

모든 컴포넌트에서 쓰는 기본기 — useState, useEffect, props, key, 제어 입력 — 뿐 아니라 Actions 기반 폼 패턴을 포함한 최신 React 19 추가 사항까지 다루므로, 복습용으로도 최신 API로 넘어가는 다리로도 활용할 수 있습니다.

이 시트는 무료이며 클라이언트 사이드에서 동작합니다. 검색창으로 훅과 패턴을 실시간 필터링하고, 고정 목차로 섹션 간 이동하고, 클릭 한 번으로 스니펫을 복사하고, 컴포넌트 작업 중 참고용으로 페이지를 인쇄할 수 있습니다.

React 치트시트 사용 방법

컴포넌트 및 JSX와 상태 및 이펙트부터 React 19 훅 및 API와 성능까지 섹션을 훑어봅니다.
useEffect, key, context 같은 훅이나 개념을 검색해 시트를 실시간으로 필터링합니다.
특정 패턴이 필요할 때 고정 사이드바로 폼 및 Actions나 ref 섹션으로 이동합니다.
스니펫이나 복사 아이콘을 클릭해 코드를 컴포넌트에 복사합니다.
오프라인 React 참고용으로 시트를 인쇄합니다.

자주 묻는 질문

네. 오래된 기본기 외에도 React 19 전용 훅과 API 섹션, 그리고 최신 Actions 패턴을 중심으로 만든 폼 섹션이 별도로 있습니다.

열두 개 섹션입니다: 컴포넌트와 JSX, 렌더링과 설정, 상태와 이펙트, React 19 훅과 API, 폼과 Actions, props와 컴포지션, 이벤트, 리스트와 키, 컨텍스트, ref, 성능, 메타데이터 및 기타입니다.

네. 상태 및 이펙트 섹션에서는 useState와 useEffect의 흔한 변형까지 함께 보여주며, 컨텍스트, ref, 성능 섹션에서는 각 주제에 해당하는 훅을 다룹니다.

네. 어떤 코드 스니펫이나 호버 복사 아이콘을 클릭하면 클립보드에 복사되고 짧은 확인 메시지가 뜹니다.

네, 완전 무료입니다 — 검색과 인쇄가 가능하고 브라우저에서 렌더링되며 가입도 필요 없습니다.

React 치트시트

Components & JSX

Rendering & setup

State & effects

React 19 hooks & APIs

Forms & Actions

Props & composition

Events

Lists & keys

Context

Refs

Performance

Misc & metadata

React 치트시트 소개

React 치트시트 사용 방법

자주 묻는 질문

이 치트시트는 React 19 기준으로 최신인가요?

어떤 주제를 다루나요?

핵심 훅도 다루나요?

스니펫을 한 번에 복사할 수 있나요?

React 참고 자료는 무료인가요?

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