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Stacked on #32783. This will replace [the `useSwipeTransition` API](https://github.com/facebook/react/pull/32373). Instead, of a special Hook, you can make updates to `useOptimistic` Hooks within the `startGestureTransition` scope. ``` import {unstable_startGestureTransition as startGestureTransition} from 'react'; const cancel = startGestureTransition(timeline, () => { setOptimistic(...); }, options); ``` There are some downsides to this like you can't define two directions as once and there's no "standard" direction protocol. It's instead up to libraries to come up with their own conventions (although we can suggest some). The convention is still that a gesture recognizer has two props `action` and `gesture`. The `gesture` prop is a Gesture concept which now behaves more like an Action but 1) it can't be async 2) it shouldn't have side-effects. For example you can't call `setState()` in it except on `useOptimistic` since those can be reverted if needed. The `action` is invoked with whatever side-effects you want after the gesture fulfills. This is isomorphic and not associated with a specific renderer nor root so it's a bit more complicated. To implement this I unify with the `ReactSharedInternal.T` property to contain a regular Transition or a Gesture Transition (the `gesture` field). The benefit of this unification means that every time we override this based on some scope like entering `flushSync` we also override the `startGestureTransition` scope. We just have to be careful when we read it to check the `gesture` field to know which one it is. (E.g. I error for setState / requestFormReset.) The other thing that's unique is the `cancel` return value to know when to stop the gesture. That cancellation is no longer associated with any particular Hook. It's more associated with the scope of the `startGestureTransition`. Since the schedule of whether a particular gesture has rendered or committed is associated with a root, we need to somehow associate any scheduled gestures with a root. We could track which roots we update inside the scope but instead, I went with a model where I check all the roots and see if there's a scheduled gesture matching the timeline. This means that you could "retain" a gesture across roots. Meaning this wouldn't cancel until both are cancelled: ``` const cancelA = startGestureTransition(timeline, () => { setOptimisticOnRootA(...); }, options); const cancelB = startGestureTransition(timeline, () => { setOptimisticOnRootB(...); }, options); ``` It's more like it's a global transition than associated with the roots that were updated. Optimistic updates mostly just work but I now associate them with a specific "ScheduledGesture" instance since we can only render one at a time and so if it's not the current one, we leave it for later. Clean up of optimistic updates is now lazy rather than when we cancel. Allowing the cancel closure not to have to be associated with each particular update. |
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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 own 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 Quick Start to get a taste of React.
- Add React to an Existing Project to use as little or as much React as you need.
- Create a New React App if you're looking for a powerful JavaScript toolchain.
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:
- Quick Start
- Tutorial
- Thinking in React
- Installation
- Describing the UI
- Adding Interactivity
- Managing State
- Advanced Guides
- API Reference
- Where to Get Support
- Contributing Guide
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.
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.