🧪 Add ReactTestRenderer.act() and ReactTestUtils.act()

Two new test helpers are now available for batching updates so that tests more closely match the real behavior.

https://github.com/facebook/react/pull/14744

⏰ Scheduler.unstable_next()

A new unstable API was added to the Scheduler to queue a task with a lower priority than the default priority of interaction callbacks. This allows CPU or IO-heavy work to run after the UI responds.

https://github.com/facebook/react/pull/14756

⏮ Backwards Compat Fix for ReactCurrentDispatcher

A previous pull request caused issues when combining newer renderers with a version of the react package that predated the change. This is now fixed.

https://github.com/facebook/react/pull/14770

📌 React v16.8.1 Patch Release

After the big v16.8 release, the team also worked on some smaller bug fixes which are now out as well. Thank you for your hard work!

https://github.com/facebook/react/blob/master/CHANGELOG.md#1681-february-6-2019

☕️ React as a UI Runtime

In this comprehensive article, Dan (@gaearon) wrote a lot about the internals of React. I highly recommend this read: https://overreacted.io/react-as-a-ui-runtime/

🏞 Partial Hydration

The partial hydration PR has now landed in master. This new mode can start hydrating a server rendered result while some parts are still loading. The goal is decrease the time to interactive.

https://github.com/facebook/react/pull/14717

📚 Component Stack in act() Warning

The warning about missing act() wrapping in some test environments now contains a component stack trace.

https://github.com/facebook/react/pull/14855

🖥 Fix SSR Context Leaks When Render Stream Destroyed Early

This PR fixes a Context memory leak in the SSR if a stream is destroyed before the render completes.

https://github.com/facebook/react/pull/14706

📡 Properly Support crossOrigin for SVG Images

We now properly case the crossOrigin property that’s used for SVG image elements.

https://github.com/facebook/react/pull/14832

👀 Fix useImperativeHandle Without Dependencies

The useImperativeHandle hook now properly behaves like no dependencies were set when the second argument is omitted.

https://github.com/facebook/react/pull/14801

📌 React v16.8.2 Patch Release

This release brings bug fixes and stability improvements around hooks and other features.

https://github.com/facebook/react/blob/master/CHANGELOG.md#1682-february-14-2019

📌 Add eslint-plugin-react-hooks/exhaustive-deps

The ESLint plugin for React hooks now has a new exhaustive-deps rule that verifies that the proper dependency array is specified. It also warns when assigning a to variable from an outside closure.

https://github.com/facebook/react/pull/14636

🤹‍♀️ act() Examples

Sunil (threepointone) created notes that explains the necessity of the new act() API for writing tests that should resemble production behavior.

https://github.com/threepointone/react-act-examples

🗺 RFC: createElement Changes

A new RFC outlines changes to React.createElement() that simplifies the object representation and will also allow forwardRef to be removed in the future.

https://github.com/reactjs/rfcs/pull/107

🌍 New React Internationalization Repo: Greek

The list of internationalization repos is still growing. This week, we’re adding the Greek repository.

https://github.com/reactjs/el.reactjs.org

🕳 Deal with Fallback Content in Partial Hydration

This PR allows a dehydrated suspense boundary to be in three possible states (as encoded with different comment nodes).

https://github.com/facebook/react/pull/14884

🐞 Fix UMD Builds by Re-exporting the Scheduler Priorities

A recent regression caused the v16.8.2 release to break input elements when using the UMD build. This was fixed by properly exporting the Scheduler priorities.

https://github.com/facebook/react/pull/14914

📌 React v16.8.3 Patch Release

This release fixes several bugs around React DOM.

https://github.com/facebook/react/releases/tag/v16.8.3

🌏 Is React Translated Yet? ¡Sí! Sim! はい！

A new blog post explains the React documentation internationalization effort and mentions the first three live websites: Spanish, Japanese, and Brazilian Portuguese.

https://reactjs.org/blog/2019/02/23/is-react-translated-yet.html

💼 RFC: Focus Management API

Devon Govett (devongovett) worked on an RFC for a new API to improve focus handling in React. Feedback welcome!

https://github.com/reactjs/rfcs/pull/109

⏱ Add New Mock Build of Scheduler

To control the Scheduler queue in test environments, a new mock version of the Scheduler was added.

https://github.com/facebook/react/pull/14964