react v18.1.0 Release Notes
Release Date: 2022-04-26 // 28 days ago-
React DOM
- π Fix the false positive warning about
react-dom/client
when using UMD bundle. (@alireza-molaee in #24274) - π Fix
suppressHydrationWarning
to work in production too. (@gaearon in #24271) - π Fix
componentWillUnmount
firing twice inside of Suspense. (@acdlite in #24308) - π Fix some transition updates being ignored. (@acdlite in #24353)
- π Fix
useDeferredValue
causing an infinite loop when passed an unmemoized value. (@acdlite in #24247) - π Fix throttling of revealing Suspense fallbacks. (@sunderls in #24253)
- π Fix an inconsistency in whether the props object is the same between renders. (@Andarist and @acdlite in #24421)
- π Fix a missing warning about a
setState
loop inuseEffect
. (@gaearon in #24298) - π Fix a spurious hydration error. (@gnoff in #24404)
- Warn when calling
setState
inuseInsertionEffect
. (@gaearon in #24295) - Ensure the reason for hydration errors is always displayed. (@gaearon in #24276)
React DOM Server
- π Fix escaping for the
bootstrapScriptContent
contents. (@gnoff in #24385) - π Significantly improve performance of
renderToPipeableStream
. (@gnoff in #24291)
π ESLint Plugin: React Hooks
- π Fix false positive errors with a large number of branches. (@scyron6 in #24287)
- Don't consider a known dependency stable when the variable is reassigned. (@afzalsayed96 in #24343)
π Use Subscription
- π Fix the false positive warning about
Previous changes from v18.0.0
-
π Below is a list of all new features, APIs, deprecations, and breaking changes. π Read React 18 release post and React 18 upgrade guide for more information.
π New Features
React
useId
is a new hook for generating unique IDs on both the client and server, while avoiding hydration mismatches. It is primarily useful for component libraries integrating with accessibility APIs that require unique IDs. This solves an issue that already exists in React 17 and below, but itβs even more important in React 18 because of how the new streaming server renderer delivers HTML out-of-order.- β‘οΈ
startTransition
anduseTransition
let you mark some state updates as not urgent. Other state updates are considered urgent by default. React will allow urgent state updates (for example, updating a text input) to interrupt non-urgent state updates (for example, rendering a list of search results). - π
useDeferredValue
lets you defer re-rendering a non-urgent part of the tree. It is similar to debouncing, but has a few advantages compared to it. There is no fixed time delay, so React will attempt the deferred render right after the first render is reflected on the screen. The deferred render is interruptible and doesn't block user input. - β‘οΈ
useSyncExternalStore
is a new hook that allows external stores to support concurrent reads by forcing updates to the store to be synchronous. It removes the need foruseEffect
when implementing subscriptions to external data sources, and is recommended for any library that integrates with state external to React. - π
useInsertionEffect
is a new hook that allows CSS-in-JS libraries to address performance issues of injecting styles in render. Unless youβve already built a CSS-in-JS library we donβt expect you to ever use this. This hook will run after the DOM is mutated, but before layout effects read the new layout. This solves an issue that already exists in React 17 and below, but is even more important in React 18 because React yields to the browser during concurrent rendering, giving it a chance to recalculate layout.
React DOM Client
These new APIs are now exported from
react-dom/client
:createRoot
: New method to create a root torender
orunmount
. Use it instead ofReactDOM.render
. New features in React 18 don't work without it.hydrateRoot
: New method to hydrate a server rendered application. Use it instead ofReactDOM.hydrate
in conjunction with the new React DOM Server APIs. New features in React 18 don't work without it.
0οΈβ£ Both
createRoot
andhydrateRoot
accept a new option calledonRecoverableError
in case you want to be notified when React recovers from errors during rendering or hydration for logging. By default, React will usereportError
, orconsole.error
in the older browsers.React DOM Server
π These new APIs are now exported from
react-dom/server
and have full support for streaming Suspense on the server:renderToPipeableStream
: for streaming in Node environments.- π·
renderToReadableStream
: for modern edge runtime environments, such as Deno and Cloudflare workers.
The existing
renderToString
method keeps working but is discouraged.