🌎 React Docs Language Switcher

With the release of the first three localizations (see above), the documentations now also feature a language switcher

https://reactjs.org/languages

🛠 DevTools: Support Editable useState Hooks

To allow a future DevTools version to edit useState hooks, a new overrideHookState was added to work with react-debug-tools.

https://github.com/facebook/react/pull/14906

🌍 6 New React Internationalization Repos

With six new internationalization repos added last week, we’re now at a total of 38. This week brings:
- Gujarati: reactjs/gu.reactjs.org
- Central Khmer: reactjs/km.reactjs.org
- Kurdish: reactjs/ku.reactjs.org
- Lithuanian: reactjs/lt.reactjs.org
- Telugu: reactjs/te.reactjs.org
- Urdu: reactjs/ur.reactjs.org

⏳ Scheduler: Pass didTimeout to Callbacks

To avoid unnecessary checks to shouldYield, Scheduler callbacks now receive a didTimeout argument.

https://github.com/facebook/react/pull/14931

🎣 ESLint: Allow Extraneous Effect Dependencies

In the ESLint rule for hooks, it’s now allowed to pass dependencies that are not used inside the effect to the dependency array. Check out the PR for an example of when this is useful.

https://github.com/facebook/react/pull/14967

⚓️ ESLint: More Cases For exhaustive-deps Rule

This PR improves messaging for when you try to pass literals. Additionally it now warns when ref.current is used in an effect cleanup that it assumes is a component ref.

https://github.com/facebook/react/pull/14930

📌 ESLint: Allow Omitting Constant Primitive Deps

The eslint-plugin-react-hooks/exhaustive-deps lint rule now allows you to omit defining constant primitives (e.g. const a = 123;) in the dependencies array if you close over them.

https://github.com/facebook/react/pull/14959

🐛 Fix Compatibility Between react-debug-tools and useContext()

react-debug-tools is an experimental package for debugging React renderers. This PR fixes a bug that was causing issues with this package and useContext().

https://github.com/facebook/react/pull/14940

🔎 eslint-plugin-react-hooks v1.5.0

The ESLint plugin exhaustive-deps is now in a good shape to be adopted in most projects. Install it and report back any issues! A few of the changes can be found down below.

https://twitter.com/dan_abramov/status/1103744582074990594

🐞 New DevTools Architecture Overview

Brian updated the new DevTools Architecture Overview with the goal of minimizing bridge traffic and avoid serialization overhead.

https://github.com/bvaughn/react-devtools-experimental/blob/master/OVERVIEW.md

🚀 Scheduling in React

I wrote an article about why we need Scheduling in React. Make sure to also check out Dan’s comments.

https://philippspiess.com/scheduling-in-react/

🌏 New React Docs Localizations Live

This week, four new React documentation websites went live:
• French: fr.reactjs.org
• Russian: ru.reactjs.org
• Ukrainian: uk.reactjs.org
Simplified Chinese: zh-hans.reactjs.org
At the same time, two new localization repos where added:
• Swedish: reactjs/sv.reactjs.org
• Thai: reactjs/th.reactjs.org

📌 ESLint: Warn about Dependencies Outside of Render Scope

Variables that are defined outside of the render scope (for example global variables like window) do not cause a component to re-render when they’re mutated. This doesn’t play together with the dependency array so the ESLint rule exhaustive-deps now warns in those cases.

https://github.com/facebook/react/pull/14990

⏳ Import Scheduler Directly

With the introduction of a general purpose scheduler, the individual React renders can now directly call the unified Scheduler APIs. Read the PR denoscription for a good overview of the current situation!

https://github.com/facebook/react/pull/14984

⚠️ Warn When Dependencies Are Not an Array

React now warns on mounting a component that uses hooks where the dependencies are not an array.

https://github.com/facebook/react/pull/15018

⚓️ ESLint: Treat Functions That Don’t Capture Anything As Static

For the exhaustive-deps ESLint rule, functions that do not capture anything are now treated as static. Even if they close over a setState() function that comes from the useState() hook.

https://github.com/facebook/react/pull/14996

🎣 ESLint: Enforce Dependencies Array in useMemo and useCallback

The ESLint rule will now also enforce a dependencies array when useMemo() or useCallback() is used.

https://github.com/facebook/react/pull/15025

📌 React v16.8.4 Patch Release

This release includes a bug fix that sometimes caused a runtime error when DevTools are open

https://github.com/facebook/react/releases/tag/v16.8.4

🍱 A Complete Guide to useEffect

Dan wrote another extensive blog post which goes into the nitty gritty details of the useEffect hook. Highly recommended!
https://overreacted.io/a-complete-guide-to-useeffect/

⚠️ Warn for javanoscript: URLs in DOM Sinks

javanoscript: URLs in DOM sinks are a possible attack vector for XSS attacks. This PR adds a warning when using those for the remainder of 16.x releases.
https://github.com/facebook/react/pull/15047

📱 Infrastructure for Passive/Non-Passive Event Experiments

To explore future APIs, this PR is adding infrastructure to allow registration for passive/non-passive events in the event system. Please note that this is currently in the experimentation phase and it might take some time until these APIs are available.
https://github.com/facebook/react/pull/15036