📝 Add Suspense and lazy() to API Docs

The latest stable release of React brings lazy() and Suspense. These features are now referenced in the API docs as well.
https://github.com/reactjs/reactjs.org/pull/1446

👋 Remove useMutationEffect

The useMutationEffect hook had a major flaw: Element refs were not initialized when they were fired. Read the PR for more information why this hook was removed.
https://github.com/facebook/react/pull/14336

👩‍🏫 Validate propTypes for lazy() and memo()

The previous implementation of React.lazy() and React.memo() did not take propTypes into account. From now on, this works as expected.
https://github.com/facebook/react/pull/14298

🏞 New Server Rendering Infrastructure: Fizz

Work on the new Server Rendering Infrastructure Fizz has begun. The new renderer features built in support for Suspense and utilizes node streams. Check out Andrew’s talk at ZEIT earlier this year for a glimpse of what the new server renderer will be able to do.
https://github.com/facebook/react/pull/14144

🔥 WIP: Base Implementation of React Fire

You can now follow along as the team is preparing the React DOM code for the upcoming React Fire updates. The changes currently include a new and lighter weight event system.
https://github.com/facebook/react/pull/14382

⏱ Implement pauseExecution, continueExecution, and dumpQueue for Scheduler

Kevin Chavez (mrkev) added three new methods to the Scheduler package to make it simpler to build debugger tools in the browser.
https://github.com/facebook/react/pull/14053

🐶 Automated Fixture Tests

Some of the manual fixtures are now tested automatically with the help of Puppeteer, an automation helper for Chromium.
https://github.com/facebook/react/pull/14370

⏳ Fixed Scheduler setTimeout Fallback

An issue in the Scheduler package caused useEffect to be broken in React Native with JavaScript Core.
https://github.com/facebook/react/pull/14358

🛥 Avoid a V8 Performance Cliff When Profiling

Thanks to the help of V8 team members, the React team was able to find and fix a significant performance cliff during the commit phase when the React profiler is enabled.
https://github.com/facebook/react/pull/14383

📌 Enable Hooks In Fabric

Fabric is the ongoing large-scale architectural rewrite of React Native. You can learn more about it in the State of React Native 2018 blog post.
https://github.com/facebook/react/pull/14301

🚸 RFC: Fragment Refs

Fragment refs are presented as an alternative to findDOMNode(). They would allow you to receive an array of DOM nodes rendered by children.
https://github.com/reactjs/rfcs/pull/97

🗂 RFC: Custom Host Node

Custom Host Nodes are an alternative to the useMutationEffect() API that was originally part of the hooks RFC but got removed later on.
https://github.com/reactjs/rfcs/pull/96

💬 Discussion: Provide Ways to Bail out Inside Hooks

Some use cases require function components with hooks to bail out early. The discussion gives insights into when this is needed. Make sure to check out Sebastian’s latest response on this topic.
https://github.com/facebook/react/issues/14110

📌 Mention Hooks As Accepted on the Website

The React Hooks RFC has recently been merged. Thanks to Jamie (jamiebuilds), the website is now updated to reflect this as well.
https://github.com/reactjs/reactjs.org/pull/1485

🔎 Add <Suspense> and lazy() to react-is

Pleun Vanderbauwhede (pleunv) added support for <Suspense> and lazy() to react-is. This package is used to test for particular React element types.
https://github.com/facebook/react/pull/14423

💉 Inject overrideProps() into DevTools

Development builds are now exposing a new function to the DevTools which is required to allow editing props of more component types.
https://github.com/facebook/react/pull/14427

🎉 React 16.7 Release

No, This Is Not The One With Hooks, but this release contains non-trivial changes to fix various performance issues. Read the accompanying release blog post for more details.
https://reactjs.org/blog/2018/12/19/react-v-16-7.html

📋 Memoize Promise Listeners

Previously, React attached new listeners whenever a promise was thrown. This was causing special headaches in non-concurrent mode, where React re-renders immediately after a promise is thrown, causing exponential growth of promise listeners.
https://github.com/facebook/react/pull/14429

🛠 DevTools: Support Editable Props for More Component Types

In the upcoming DevTools release, you’ll be able to edit the props of more component types including function components, host elements, and special types like context providers, memo, and forwardRef. Check out the pre-release build.
https://github.com/facebook/react-devtools/pull/1249

📌 WIP: Support Hooks in DevTools

Support for Hooks in DevTools allows you to inspect useState state values, useCallback functions, and even deeply nested custom hooks.
While the core team is getting hooks ready for a stable release, this work in progress pull request gives an early glimpse of the new DevTools integration.

https://github.com/facebook/react-devtools/pull/1272

➡️ Rename useImperativeMethods to useImperativeHandle

The hook to customize the instance value that is exposed to parent components when using ref is now called useImperativeHandle.

https://github.com/facebook/react/pull/14565