👋 Remove <React.unstable_ConcurrentMode />

Partial opt-in into Concurrent Mode creates edge cases that are not trivial to support. Instead, the recommended approach is to opt in the entire root.

https://github.com/facebook/react/pull/15532

🧪 Flush the Scheduler Manually inside act()

With this PR, the act() test helper is now manually flushing the Scheduler using Scheduler.unstable_flushWithoutYielding internally.

https://github.com/facebook/react/pull/15591

🕹 Fix Serial Passive Effects

This change makes sure that passive effects are flushed before discrete event handlers are called.

https://github.com/facebook/react/pull/15650

⏲ Remove Scheduler from React Package Dependencies

The isomorphic react package no longer depends directly on the scheduler. Now, only the individual renderers (e.g. react-dom) do.

https://github.com/facebook/react/pull/15616

🙅‍♀️ Invariant When Committing Wrong Tree

This change adds a new invariant that throws if the new tree is the same as the old one.

https://github.com/facebook/react/pull/15517

🎇 React Flare Updates

Another week of great improvements for the experimental event API that the team at Facebook is working on. preventDefault now work for nested updates, a pointerType was added to to Focus events, getFocusableElementsInScope handles suspended trees, and more.

https://github.com/facebook/react/issues/15257

🛑 Bail out of Updates in Offscreen Trees

With this change, sync updates inside hidden trees are now delayed when using Concurrent Mode.

https://github.com/facebook/react/pull/15666

🎫 Upcoming GitNation Events

While we are here, I want to point out a few of the upcoming events from the fantastic folks at GitNation. If you have the chance, I recommend checking out one of their conferences this year:
• JS Nation, Amsterdam, June 5–7
• React Advanced, London, Oct 25
• React Day Berlin, Berlin, Dec 6

🔄 React Fresh

The team started to work on React Fresh, a new generation of hot reloading. Changes include initial scaffolding, infrastructure, and Babel plugin implementation

Check out this Tweet by Dan Abramov for a teaser and some insights:
https://twitter.com/dan_abramov/status/1126948870137753605?s=20

🛠 Inform DevTools of Commit Priority Level

React now exposes information about the commit priority level to DevTools.

https://github.com/facebook/react/pull/15664

🧪 Flush Only on Exiting Outermost act()

act() will now only flush on exiting the outermost callback. This changes the behavior of nested act()s.

https://github.com/facebook/react/pull/15682

🇭🇺 Hungarian Localization

You can now help translate the official React documentations to Hungarian.

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

👷‍♀️ Parallelize CircleCI Jobs Using Workflows

The React repository CI tests now using the CircleCI Workflows feature. This improves status reporting in GitHub.

https://github.com/facebook/react/pull/15704

🎇 React Flare Updates

This week also brings more work on React Flare. There are updated interactiveUpdates flushing heuristics, getAbsoluteBoundingClientRect now accounts for fixed elements, getEventCurrentTarget now uses the fiber tree, and more.

https://github.com/facebook/react/issues/15257

🚧 Set Up Cron Job for Fuzz Tester

The fuzz tester is now run on CI periodically with a randomly generated seed.

https://github.com/facebook/react/pull/15718

🐛 Fix Missing Return Pointer Assignment

This change fixes an issue in the fiber code by assign the missing return pointer correctly.

https://github.com/facebook/react/pull/15700

🛤 Path-Based Imports for RN Renderer

React Native is moving to path-based imports from the globally-unique-named Haste system.

https://github.com/facebook/react/pull/15604

🇪🇺 ReactEurope Recap

I’m writing today’s newsletter from ReactEurope in Paris and there are so many amazing talks. You can catch up by looking at my Twitter thread.

https://twitter.com/PhilippSpiess/status/
1131457729250385921

React State with Hooks: useReducer, useState, useContext

If you haven’t used state management excessively in React Function Components, this tutorial may help you to get a better understanding of how React Hooks – such as useState, useReducer, and useContext – can be used in combination for impressive state management in React applications. In this tutorial, you'll almost reach the point where these hooks mimic sophisticated state management libraries like Redux for globally managed state. Let’s dive into the application which you'll implement together step by step.

Creating Your Own React Validation Library: The Basics (Part 1)

This article takes you through how to implement your own form validation library step by step. There’s plenty of interactive examples, and it’s easy to follow along.

🔥 An Update on React Fire
Dan recently posted an update on React Fire to the GitHub issue. It mentions recent experiments like React Flare and how the work on these features impacts the React Fire plan.

https://github.com/facebook/react/issues/13525#issuecomment-499196939