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* Add `isHidden` to OffscreenInstance We need to be able to read whether an offscreen tree is hidden from an imperative event. We can store this on its OffscreenInstance. We were already scheduling a commit effect whenever the visibility changes, in order to toggle the inner effects. So we can reuse that. * [FORKED] Bugfix: Revealing a hidden update This fixes a bug I discovered related to revealing a hidden Offscreen tree. When this happens, we include in that render all the updates that had previously been deferred — that is, all the updates that would have already committed if the tree weren't hidden. This is necessary to avoid tearing with the surrounding contents. (This was the "flickering" Suspense bug we found a few years ago: #18411.) The way we do this is by tracking the lanes of the updates that were deferred by a hidden tree. These are the "base" lanes. Then, in order to reveal the hidden tree, we process any update that matches one of those base lanes. The bug I discovered is that some of these base lanes may include updates that were not present at the time the tree was hidden. We cannot flush those updates earlier that the surrounding contents — that, too, could cause tearing. The crux of the problem is that we sometimes reuse the same lane for base updates and for non-base updates. So the lane alone isn't sufficient to distinguish between these cases. We must track this in some other way. The solution I landed upon was to add an extra OffscreenLane bit to any update that is made to a hidden tree. Then later when we reveal the tree, we'll know not to treat them as base updates. The extra OffscreenLane bit is removed as soon as that lane is committed by the root (markRootFinished) — at that point, it gets "upgraded" to a base update. The trickiest part of this algorithm is reliably detecting when an update is made to a hidden tree. What makes this challenging is when the update is received during a concurrent event, while a render is already in progress — it's possible the work-in-progress render is about to flip the visibility of the tree that's being updated, leading to a race condition. To avoid a race condition, we will wait to read the visibility of the tree until the current render has finished. In other words, this makes it an atomic operation. Most of this logic was already implemented in #24663. Because this bugfix depends on a moderately risky refactor to the update queue (#24663), it only works in the "new" reconciler fork. We will roll it out gradually to www before landing in the main fork. * Add previous commit to list of forked revisions
React · 
React is a JavaScript library for building user interfaces.
- Declarative: React makes it painless to create interactive UIs. Design simple views for each state in your application, and React will efficiently update and render just the right components when your data changes. Declarative views make your code more predictable, simpler to understand, and easier to debug.
- Component-Based: Build encapsulated components that manage their state, then compose them to make complex UIs. Since component logic is written in JavaScript instead of templates, you can easily pass rich data through your app and keep the state out of the DOM.
- Learn Once, Write Anywhere: We don't make assumptions about the rest of your technology stack, so you can develop new features in React without rewriting existing code. React can also render on the server using Node and power mobile apps using React Native.
Learn how to use React in your project.
Installation
React has been designed for gradual adoption from the start, and you can use as little or as much React as you need:
- Use Online Playgrounds to get a taste of React.
- Add React to a Website as a
<script>tag in one minute. - Create a New React App if you're looking for a powerful JavaScript toolchain.
You can use React as a <script> tag from a CDN, or as a react package on npm.
Documentation
You can find the React documentation on the website.
Check out the Getting Started page for a quick overview.
The documentation is divided into several sections:
You can improve it by sending pull requests to this repository.
Examples
We have several examples on the website. Here is the first one to get you started:
import { createRoot } from 'react-dom/client';
function HelloMessage({ name }) {
return <div>Hello {name}</div>;
}
const root = createRoot(document.getElementById('container'));
root.render(<HelloMessage name="Taylor" />);
This example will render "Hello Taylor" into a container on the page.
You'll notice that we used an HTML-like syntax; we call it JSX. JSX is not required to use React, but it makes code more readable and writing it feels like writing HTML. If you're using React as a <script> tag, read this section on integrating JSX; otherwise, the recommended JavaScript toolchains handle it automatically.
Contributing
The main purpose of this repository is to continue evolving React core, making it faster and easier to use. Development of React happens in the open on GitHub, and we are grateful to the community for contributing bugfixes and improvements. Read below to learn how you can take part in improving React.
Code of Conduct
Facebook has adopted a Code of Conduct that we expect project participants to adhere to. Please read the full text so that you can understand what actions will and will not be tolerated.
Contributing Guide
Read our contributing guide to learn about our development process, how to propose bugfixes and improvements, and how to build and test your changes to React.
Good First Issues
To help you get your feet wet and get you familiar with our contribution process, we have a list of good first issues that contain bugs that have a relatively limited scope. This is a great place to get started.
License
React is MIT licensed.