Seb ⚛️ ThisWeekInReact.com
@sebastienlorber
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🔥 Join 40k devs - Stay up-to-date with React: • 📨 https://t.co/DvLGHeLY5G • @ThisWeekInReact • @docusaurus maintainer • 🇫🇷
Joined May 2009
This Week In React 238. Read and subscribe here!. ⚛️.- React Router.- RSC.- shadcn/ui.- TanStack Start.- React Aria.- ForesightJS.- Cosmos.📱.- iOS 26.- JSI setRuntimeData.- Windows.- Nitro.- WebView.- Bottom Tabs.- PencilKit
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Next.js middleware checking request auth
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🧑🎄 Node.js now supports TypeScript by default 🤯 🎄
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TIL about timing attacks with an easy-to-understand JS example
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😄 Top-tier React meme found on Reddit. I didn't get it at first
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ESLint:.⚠️ "Nesting ternary expressions can make code more difficult to understand.". TypeScript:
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React + TypeScript tip. No need to import DOM event handler types. This always works and is easy to remember
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TIL React 18 will allow returning undefined.
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💡 React devs, it's time to start using Array.prototype.with(). The easy way to replace an existing element in a React state array. Much more convenient than array.splice/map 👌. ✅ ES stage-4.✅ available in latest browsers.⚠️ 82% caniuse support.✅ polyfills
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The main Shopify Mobile app ➡️ being migrated to React-Native, . @mauriciom shares the story. 6 years old app - 300+ screens. First approach didn't work.New approach: rewrite starting from app root . Video: before/after of app root. Benefits + Challenges.
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React 19 greatly simplify vanilla data fetching. Previously we had to useEffect, handle race conditions, unmounts, loading/error state. Now you just:.- store a promise .- read it within Suspense/ErrorBoundary. This makes a whole class of problems disappear
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TIL this GitHub Actions trick. When a PR has multiple consecutive commits (ie fixing typos 😏). ➡️ these 3 lines save resources and cancel previous useless CI runs. via @bitandbang @targos89 in Node.js PR:
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Took me 10+ years to discover that form elements have a "form" attribute 😅. And can be used outside of the parent <form> element natively.
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There are 16 hooks in React 😏 😈. And I bet you never used this one: useSyncExternalStore(). Used internally in state management libs, like Redux . But have you ever thought about using it in your own app code?. 💡 It could be useful & even prevent some React re-renders . 👇 🧵
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🤯 ByteDance just announced Lynx, their native cross-platform technology. Used extensively in their apps, including TikTok!. With first-class React bindings, it's serious competitor to React Native. The architectural choices are really interesting, with a dual-thread model
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React useSyncExternalStore + localStorage = 🔥. Pretty cool what you can do. Here the Docusaurus theme sync with localStorage value:.- between 2 distinct windows.- for each embedded iframe of each window
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👀 React-Forget is coming?. React DevTools v5.0 shows a new Forget badge now. Instagram web uses React Forget already.Not sure FB uses it yet.
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Who's next 😂
new paper on a vulnerability discovered in React Router, resulting from a collaboration with @inzo____ that led to CVE-2025-31137;. React Router and the Remix'ed path. good reading
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👀 Official useOpaqueIdentifier() hook in React-18.
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😱 Records & Tuples is an awesome TC39 proposal. 🤯 It could have a huge impact on JS, and React. 🐛 issues it could help to solve:.- performance.- behavior.- more explicit API surface. Discover how Records & Tuples will improve React:.
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TypeScript + React. This code used to fail due to destructuring.In TS 4.6, this will now work fine .
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Curious, did you ever had to use this pattern in React?. queueMicrotask: executes synchronously after all layout effects have been executed. I find this pattern useful in some very specific situations. For example, restoring a scroll position after layout updates
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TypeScript 4.6 released:. Major control-flow-analysis improvements, very useful for React. The following code will now compile fine 👌
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Twitter finally has an official JavaScript / TypeScript SDK.
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React Compiler - Release Candidate 🙌.
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📦 ForesightJS - Modern way to prefetch your data. This cool library predicts cursor moves to prefetch elements earlier. Docs show how to use with Next.js and React Router link components. Better than waiting for hover 👌.Even supports predictive tab keyboard nav 😄
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This JS is going to be standardized as ES2025 🎉. Already supported by: .- Node 22 .- Chrome 122 .- TypeScript 5.6
ECMAScript excitement 😉. Congrats to @smooshMap on advancing the Iterator Helpers proposal to Stage 4 at @TC39 today 🎉.
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⚛️ React DevTools v6.0. They received a ton of work recently!. Notably for integrating RSCs .Presenting a unified React component tree 👌. Browser extensions not yet been published. But changelog is here with many PRs/screenshots.
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Lesson learned. ❌ Don't use free domain names in your code/docs . A malicious Turkish Casino might buy that domain 😅
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🛑 React SSR - Don't do this:. useState(() => {. if (typeof window !== "undefined") {. return localStorage.getItem("xyz"). }. return fallback;.}) . 🐛 Leads to hydration mismatches. useSyncExternalStore ➡️ good way to prevent React hydration issues.
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👀 . Did I miss something or there's a new meta-framework coming 🤯
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⚛️ Server Actions have officially been renamed to Server Functions. It's in the v19 docs online now. Server Actions are now a subset of a more general Server Function feature:.- <form action={serverAction}/>.- useActionState(serverAction).- startTransition(asyncTransitionFn)
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💡 JS in 2023 ➡️ Use Error Cause. Because sometimes an error message is not precise enough. This is particularly useful to add extra context when processing a list of items. Node.js and browsers started printing the full error "causal chain" in 2022
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Iterator Helpers are almost supported everywhere 🎉. - TC39 stage 4.- TypeScript 5.6.- Node 22 .- Chrome 122 .- Firefox 131.- Safari Technology Preview 106 🆕 🔥. Unlike arrays, methods are lazy, streams can be infinite. 🚧 Iterator.range(start,end) is stage 2 👀
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This week in React. 👉 Next 11.👉 React 18 demo.👉 Storybook + Vite.👉 Jotai v1.👉 React Docs Reboot.👉 React-Native-Render-HTML.👉 Aurora.👉 Conformance.👉 Error Cause.👉 Apollo Sandbox.👉 Tailwind 2.2.👉 GraphCDN. 🧵 Details 👇.
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This week in React. 👉 React 18 updates.👉 Gatsby 4.👉 Context.👉 FileSystem routing.👉 Shadows.👉 React & RN history flashback.👉 Next.js & Vercel.👉 State Management.👉 Custom hooks readability.👉 React Native everywhere.👉 React Native windows.👉 Corepack . 🧵 Details 👇
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A little naming issue I often encounter. How do you:.- avoid one-letter names.- prevent scope variable shadowing. I want to name the variable "user" instead of "u" but the name is "already taken" by outer scope. Convoluted example here, but I'm sure you already encountered it!
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Next.js App Router Training - @about_hiroppy . Interesting resource to learn Next.js features. Interactive playground with a quite exhaustive list of features/demos.
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❌ Don't use React Query to read what's synchronous. It's not because you can use React Query that you should. This includes localStorage, but many other cases as well. Can read synchronously & subscribe to changes?.➡️ useSyncExternalStore(). No loading/error state to handle
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🔥 New React core hook ➡️ useActionState. Fix confusion/limitations of the useFormState .- Renames useFormState to useActionState .- Returns pending state .- Moves the hook to react package instead of react-dom . 👍Looks better .Now React Native devs can use it too! 🥂
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Chrome 117 just dropped with groupBy (ES stage 3). Already in Safari TP, exp flag for Firefox. Looks like it will soon become available everywhere
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🧵 This Week In React. 👉 Remix 1.0.👉 Test Selector API.👉 3D Scene.👉 Prev unnecessary renders.👉 Next.js offload scripts.👉 Tamagui cross-platform UI kit.👉 Partial hydration.👉 Lighthouse 9.👉 Cloudflare Pages.👉 Fundraisings. more in the newsletter 😉. 🧵 Details 👇.
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😄 TIL about this weird Error Boundary trick from @adevnadia. setState(() => throw e) .➡️ ensure Error boundary catch useEffect errors
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Another dev gonna have a bad time 😅. No it was not dev
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React + TypeScript 4.6 beta. The announcement blog post does not make it very explicit. The following control flow analysis now works!. ✅ No more error when accessing name or id attributes
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👀 React 19 will NOT patch fetch() anymore! 🌶🌶🌶. You will have to use React.cache() instead to avoid duplicate fetch() requests. Will Next.js 14 reimplement this temporarily, for retrocompatibility? 🤷.
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Everybody's talking about Vite right now. Nobody's looking at Rspack.But it's coming to you, React devs!. 2025 prediction - React developers will use it and love it
This is awesome, and we have an exciting change coming soon to the React ecosystem 🥳.
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🧵 React v18.0 thread. A collection of interesting tweets, thoughts, and weak signals. (not a replacement for the great official blog post). TLDR:.- nice improvements.- easy to adopt.- most importantly: new foundations for the future.
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👀 React 19 Black Magic 🎩🪄🐇. You can render in JSX:.- Context.- Promise.- Context<Promise>. You don't even need for React.use() 😄
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👀 React <ViewTransition> + DOM moveBefore(). - moveBefore() now allows React to preserve state during siblings reconciliation (experimental channel). - you can animate those stateful elements with <ViewTransition>. Quite cool 😁
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🌶️ Hot take?. useEffect() to display ephemeral feedback is an antipattern. This kind of code would be so much simpler if handled directly in your API client, with interceptors. You shouldn't rely on components to be mounted to display mutation feedback
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Damn Radix UI usage is exploding . Looks like it's the most popular React headless UI lib now
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TIL after 10y+ of JavaScript 😄. setTimeout can take extra args . And this might help avoid memory leaks
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This week in React. 👉 useRef by example.👉 Before you memo().👉 Redwood 0.26 pre-render .👉 Remotion intro.👉 Relay v11-RC.👉 React-Native-Aria.👉 Z-index.👉 TypeScript function syntaxes.👉 Babel 7.13.👉 Perf beyond bundle size.👉 Core Web Vitals & SEO. 🧵🧵🧵 Details 👇👇👇.
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🧵 This Week In React. 👉 useEvent.👉 Next.js Layouts.👉 Stitches design system.👉 Mini Next.js.👉 Remix: Edge + Deno + conf.👉 Storybook: Vite vs Webpack.👉 Markdoc.👉 react/jsx-no-leaked-render.👉 Reanimated 3.👉 Expo 45.👉 rnx-kit.👉 Tamagui. more by ✉️. 🧵 Details 👇
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🧵 This Week In React. 👉 Re-render.👉 Memo.👉 ReactQuery + ReactRouter.👉 Gatsby - Reactive Site Generator.👉 useSyncExternalStore.👉 INP.👉 Storybook.👉 TypeScript.👉 Next.js.👉 Astro.👉 Remotion.👉 Blitz.👉 LightningCSS.👉 React-Native.👉 Expo. more by ✉️. 🧵 Details 👇
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🎊🎊🎊🎊🎊🎊🎊🎊🎊🎊🎊🎊🎊🎊🎊🎊.I just published my first technical blog post ever!.🎊🎊🎊🎊🎊🎊🎊🎊🎊🎊🎊🎊🎊🎊🎊🎊. I often see tutorials and code samples fetching some API data, but none of them handle edge cases and race conditions properly.
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I'm sorry but <username>/ui is a weird lib name 😅. Surprised that @shadcn succeeded despite this.
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Difficult choice for Next.js 15 users 😄
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Flutter creator recently left Google and wrote this post. What do you think of his vision?.Particularly the Wasm-based model on the web?. (let's not bash on Flutter, we RN/web/Remotion/React devs benefit from its success through Skia)
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It's easy to overestimate people's skills here. FYI I never used any of those in significant projects 😅:.- React Server Components.- Next.js.- Remix.- React-Query.- Tailwind.- Zod.- Hermes. Last production React-Native / Expo app work ➡️ 2019 😅. Last version of Next.js I used.
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No One Ever Got Fired for Choosing React 19
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🧵 This Week In React. 👉 React 18 onRecoverableError.👉 Next.js 12.1.👉 Remix 1.2.👉 ReactNode.👉 Next.js + Co-location.👉 React-Runner.👉 Tunnel-Rat.👉 Fabric + React-Native-Screens.👉 Flipper.👉 RN crypto security.👉 Expo.👉 State Of JS.👉 Tokenizer. More by ✉️. 🧵 Details 👇.
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This week in React. 👉 many useState VS useState(obj).👉 useState => useRef.👉 hook w/ imperative APIs.👉 TS + hooks.👉 React code review.👉 Next.js conf + React Advanced.👉 Metro Exotic Transformers.👉 React-Native team Ask-Us-Anything.👉 Demo: Skia, Harmony. 🧵 Details 👇
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🧵 This Week In React ✉️. 👉 React 18 beta.👉 Remix.👉 React-Location.👉 Suspend-React.👉 Next.js RSC roadmap, improved SWC support, w/ Storybook.👉 UI lib facade.👉 StyleX.👉 Expo EAS .👉 React-Three-Fiber + RN.👉 Rust: future of JS infra?. way more by email!. 🧵 Details 👇
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Just tested and yep, here it is 👌. Error Cause (reached stage-4 recently) now works in Node.js, logging the nested stacktrace. Also works in Firefox, not yet in Chrome
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Express 5.0 was released after 10 years of alpha/beta. Can't believe we don't even have a release blog post with highlights 😅.
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💡 Missing Dan Abramov?. He just published 4 blog posts worth reading. And also re-launched this YouTube channel if you prefer videos
Don't miss the new blog post from Dan Abramov. They are all great and interactive!.
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The React Native team officially recommends Expo for all new apps 🔥. Great endorsement!. #reactconf
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I don't understand why people prefer Promise.allSettled() over Promise.all(). How often does it happen that you want to render the page if any request failed?. Like you render the page with only the footer but no header? 🤷♂️. Promise.all() by default, unless there's a good reason.
Vercel price optimization tip:.Don't block requests unnecessarily
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I don't like much Promise.all. 👉 Too sensitive to array destructuring typo. 👉 Code becomes verbose when input to transform is an object. Finally published this little utility:. 👌 TypeScript result type inference
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👀 New Vercel blog post freshly published.
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🤯 Just won an award at @ReactSummit 🥲. Thanks a lot!. Wish I was there with you all, looks like a fun conf and the place to celebrate React 10 years anniversary 🥳️
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New React core hooks to be aware of. - useFormStatus is already in Next.js and gives you the "loading state" of your Server action. - useFormState, added recently in Next.js, permits to handle the Server Action response payload. Ideal to display some feedback, notifications,
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⚛️ React Compiler news - react-compiler-runtime 🔥. A new official experimental package to support React v18 + v17 👌
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Atomic CSS-in-JS is used in production by Twitter, but also the brand new Facebook (currently in beta). Somehow, it's related to utility-first CSS like Tailwind. I wrote a post to help you understand these concepts.
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TIL React can render promises 🤯. Demo on Next.js canary 14.2:.
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Iterator Helpers - Now in all major browsers + Node.js
ECMAScript excitement 😉. Safari 18.4 ships three new @TC39 proposals 🎉. 🔶 Iterator Helpers (Stage 4).🔶 Error.isError (Stage 3).🔶 Atomics.pause (Stage 3).
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This week in React. 👉 Adobe ComboBox.👉 Remotion 2.2.👉 Gatsby 3.10.👉 React Re-rendering.👉 Suspense.👉 Bulletproof React.👉 RN Fabric.👉 React -> RN.👉 Airbnb server-driven UI.👉 TC39.👉 Firefox + Error Cause.👉 GraphQL Envelop. 🧵 Details 👇
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This week in React. 👉 React's greatest power.👉 Svelte for React experts.👉 Refs in deps.👉 Forms perfs.👉 CSS-in-JS libs analysis.👉 Next.js conf + hosting.👉 React microfrontends.👉 Cleanup effects.👉 Expo Run.👉 Coinbase TabBar.👉 WebContainers.👉 Jest 27.👉 . 🧵 Details 👇
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