React Cheat Sheet

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A searchable, printable React 19 reference — components, JSX, hooks, the new Actions APIs, context, refs and performance. Free.

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

No entry matches “:q”.

About React Cheat Sheet

This React cheat sheet targets React 19 and maps the library by concept: components and JSX, rendering and setup, state and effects, the React 19 hooks and APIs, forms and Actions, props and composition, events, lists and keys, context, refs, performance, and metadata plus miscellany.

It covers both the fundamentals you use in every component — useState, useEffect, props, keys, controlled inputs — and the newer React 19 additions, including the Actions-based form patterns, so it works as a refresher and as a bridge to the current APIs.

The sheet is free and client-side. Filter hooks and patterns live with the search box, jump between sections from the sticky table of contents, copy any snippet with one click and print the page as a reference while you build components.

How to use React Cheat Sheet

Skim the sections, from Components & JSX and State & effects to React 19 hooks & APIs and Performance.
Search for a hook or concept like useEffect, key or context to filter the sheet live.
Jump to Forms & Actions or Refs via the sticky sidebar when you need a specific pattern.
Click a snippet or its copy icon to copy the code into your component.
Print the sheet for an offline React reference.

Frequently asked questions

Yes. Alongside the long-standing fundamentals it has a dedicated React 19 hooks and APIs section and a forms section built around the newer Actions patterns.

Twelve sections: components and JSX, rendering and setup, state and effects, React 19 hooks and APIs, forms and Actions, props and composition, events, lists and keys, context, refs, performance, and metadata plus miscellany.

Yes. The state and effects section shows useState and useEffect usage with the common variants, and the context, refs and performance sections cover the hooks for each of those concerns.

Yes. Click any code snippet or its hover copy icon and it lands on your clipboard with a brief confirmation.

Yes, completely free — searchable, printable and rendered in your browser with no sign-up.

React Cheat Sheet

Components & JSX

Rendering & setup

State & effects

React 19 hooks & APIs

Forms & Actions

Props & composition

Events

Lists & keys

Context

Refs

Performance

Misc & metadata

About React Cheat Sheet

How to use React Cheat Sheet

Frequently asked questions

Is the cheat sheet current for React 19?

What topics does it cover?

Does it cover the core hooks?

Can I copy snippets with one click?

Is the React reference free?

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