This Week In React#136: Next.js, Signals, Bling, Suspense, Server Components, useSyncExternalStore, Expo, Reanimated, Metro...

Hi everyone!

This week, the debate around the signal model continues. We also have a nice release of Next.js, unveiling a new cache system to facilitate the performant usage of Server Components on a serverless Edge runtime.

A lot of activity also on the React-Native side, with Expo 48, Expo Router 1.0, Expo Image 1.0, Reanimated 3.0, and the arrival of symlinks support in Metro!

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Next.js 13.2

Next.js 13.2

A nice release with some new features that Vercel devs had already given us a preview of. The new Metadata API is useful for SEO, works well with SSR streaming, server components and the new app directory. The new Route Handlers seem to have a good usability: co-located, just export the HTTP verb. Particularly excited by the new features around MDX (Rust compiler, Server Components): that should make Next.js content sites much lighter and faster to use. If I understand correctly, Next.js starts using a TypeScript codegen step for typed links (in addition to the TypeScript plugin). Turbopack compatibility with Webpack loaders can make it easier to adopt the new bundler.

The biggest surprise for me is the introduction of a cache API directly integrated to fetch(): allows a bit the same thing as ISR but with a finer granularity, at the component level, for each request. There is even a tagging system. Next.js remains portable: the cache can be hosted on your own infrastructure, or use a local LRU cache. Of course, this is optimized for deploying on Vercel. A dedicated article gives more details and explains the limits of the ISR model: Vercel Cache API: A progressive cache, integrated with Next.js. See also the thread of Sebastian Markbåge.

The Evolution of Signals in JavaScript

The Evolution of Signals in JavaScript

This article by Ryan Carniato (SolidJS) traces the history of signals in the frontend, through KnockoutJS, MobX and many other solutions.

Signals remained the trending topic of the week. I suggest you read for yourself the many discussions that took place on Twitter:

  • Andrew Clark clarifies his position and is not closed to introducing signals into React. The React Forget compiler could compile to signals.

  • Miško Hevery explains how signals avoid perf problems on the drilling props.

  • Evan You prefers an understandable mutable model to an immutable model that leaks.

  • Devon Govett reminds us why "unidirectional data flow" was adopted and points out some problems with signals.

  • Jordan Walke mentions that they considered using a reactive model when React was created. Rejected because it changed the semantics of the language.

  • Dan Abramov explains that the user expects to see the same interface for the same data. He explains the value of using "raw values" (not wrapped in any container).

  • My position: I largely share the same views as the React team and think we need to continue to innovate on the current model, despite Signals looking attractive in the short term. I hope that eventually JavaScript will support better the immutable model, and that the React Forget compiler is only a transitional step.

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📱 React-Native

Expo 48

Expo 48

Nice release. We find back the highlights of the beta:

  • React Native 0.71.3 - React 18.2.0

  • Yoga improvements (Flexbox) that come with React-Native

  • EAS builders under M1 by default

  • Hermes engine by default

  • All Expo modules support Fabric - experimental

Some updates since the beta:

Reanimated 3.0

Reanimated 3.0

Reanimated 3.0 has just been released in a stable version, with a new Shared Elements Transitions feature (demo). It is now possible to use shared values in inline styles. The library has been rewritten to improve performance, DX and prepare for the arrival of new features. It is compatible with Fabric and the Reanimated 2 API to facilitate the upgrade, but the Reanimated 1 API has been removed.

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