Additional changes to review3 matched termsMatched wording:removeddeprecatedno longerThese matches may be harmless in context. Expand to see the excerpts.
- The changelog contains “removed”; check what was removed.
No suppression of console logs: When you use Strict Mode, React renders each component twice to help you find unexpected side effects. In React 17, we've suppressed console logs for one of the two renders to make the logs easier to read. In response to community feedback about this being confusing, we've removed the suppression. Instead, if you have React DevTools installed, the second log's renders will be displayed in grey, and there will be an option (off by default) to suppress them completely.
Below is a list of all new features, APIs, deprecations, and breaking changes. Read React 18 release post and React 18 upgrade guide for more information.
New Features
React
useIdis 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 it’s even more important in React 18 because of how the new streaming server renderer delivers HTML out-of-order.startTransitionanduseTransitionlet 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).useDeferredValuelets 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.useSyncExternalStoreis a new hook that allows external stores to support concurrent reads by forcing updates to the store to be synchronous. It removes the need for when implementing subscriptions to external data sources, and is recommended for any library that integrates with state external to React.