Name: "React 19.2: Performance and Dev Experience Upgrades" | Ali Zaib posted on the topic | LinkedIn
Uploaded: 2025-11-01T20:43:38.544Z
Duration: 4 min 58 s
Channel: Ali Zaib

Ali Zaib

6mo

🚀 React 19.2 is here — and it’s packed with smart upgrades! Just watched this quick five-minute overview, and I’m seriously impressed by how much thought has gone into performance and developer experience. From the new Activity component for smarter rendering to useEffectEvent for cleaner event logic, React keeps raising the bar. What stood out to me most: ⚡️ cacheSignal — a powerful step toward better server-component caching 🧩 Partial pre-rendering — optimizing performance right where it matters 🧠 ESLint plugin upgrade — small change, big developer quality-of-life boost It’s exciting to see React evolving in ways that make modern front-end development more intuitive and efficient. If you’re working with React, this update is worth a look — small details, big impact. #ReactJS #WebDevelopment #JavaScript #Frontend #React19 #Coding #DevTools #Performance

Transcript

React 19.2 is here and there are 6 awesome new features that you should know about because Claude code won't know them yet #4 is definitely my underrated favorite. Let's start out with a shiny new component activity. This is an alternative to conditional rendering. Say we have a sidebar, which then has an uncontrolled input on it for some reason, and two expandable sections. They're then controlled by use state hook and collapsed by default. Then in our layout, we simply use conditional rendering statement to open and close the sidebar. With this when we open the sidebar and type in some text. And then expand the sections. Then we close the sidebar and reopen it. Everything is lost as the entire component has been unmounted. If we change this logic though to use the new activity component where the conditional is actually moved to the mode prop which can either be visible or hidden with no changes to our sidebar component, you can see the one we open and close the sidebar. Now the state is being saved. This is because with activity, when the mode is visible, we acts as a normal component would. When it's hidden, it actually sets the Dom to display None, so it doesn't actually remove it and it saves our state. Values from my use state hooks, but for performance reasons it unmounts all effects and offers all updates. This makes it absolutely perfect for use cases like pre rendering. Since the component is technically rendered, just without the effect, we can still do things like fetching data. On the left is a conditionally rendered page with slow data load and the right has the exact same data load but it actually uses the activity component for our conditional rendering so the data is actually fetched before we even click on the tab. I actually did a whole video breaking down this component 2 months ago when it was experimental. So if you want to learn more, check that video out and subscribe to you're always up to date in the dev world. Next though, we also got a new hook use effect event. Let's take a look at a problem in React. In this use effect, we want to lock the URL and the counter. And I want to do that 3 seconds after the URL is changed. The problem in old React is to get the latest value of the counter, I have to have it in my dependency array. If I do that every time the counter value is updated, the three seconds is going to start all over again. But if I remove the counter from the dependency array, I violated the laws of React. Books and when we take a look at the component you can see only logs the initial value of the counter or the counter value when I changed the URL. But we want this to be the current value. So to fix this we can use the new user effect event hook. If we extract the logging into the use effect event hook and then take in the URL, then we use this new function in our use effect and leave the dependency as it is. Now the log is going to successfully be able to see the latest value of the counter after three seconds because effect events can always see the latest. Crop and state values. So TLDR is used this for things that happen to be fired from an effect instead of a user event, AKA affect events. Feature 3 is a quality of life edition for server components. To recap, you can use cash to essentially memorize expensive functions. So if two components call the same function with the same inputs during one render, React is only going to run that once. But what if React abandons or finishes the render early, for example because the user navigated away? Or maybe there was some sort of? Era those cashed async functions might still be running in the background wasting work. That's why React added cash signal. It gives you an abort signal that flips to aborted as soon as React is done with the render, whether it was cancelled or succeeded. You can then pass that signal into any async function like fetch or a database call so it stops if React no longer needs the result. OK, time for my favorite edition performance tracks. And no, I don't mean your Spotify playlist. These are actually custom tracks in Chrome Dev tools performance profiles, so you actually get more. Information about the performance of your app without even needing React dev tools. The scheduler track here shows you what React is working on for different priorities such as blocking for user interactions or transitions for updates inside of start transition. You can see here things like a user event, render and commit of the render. The components track then shows you the tree of components that React is working on either to render or run effects. It's inside you'll see labels such as mount for when children mount or affect amounted or blocked for when rendering is blocked due to yielding to work outside of React. This is going to really help you understand when components are rendered or run effects and the time it takes them to do that. Now the next feature is React Dom specific because remember React isn't always for sites, some people actually use it for roadblocks. That's not a joke by the way. The new feature is partial pre rendering is now built into React Dom. Now I won't go into the actual implementation of this as I assume it will mostly be used by framework devs, but the TLDR is you can return the prelude shell to the client AKA the static show and later call resume to continue rendering the rest. Finally, the Eslint plugin gone upgrade so it supports the new flat config as well as opt in for new React compiler powered rules. This plug-in is actually so important now as following these rules make sure that your code base can take advantage of the React compiler. If you don't know what that is, we have another video covering that as well. Seriously, if you haven't subscribed yet, you absolutely should. And as always, see you in the next one.

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