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A long standing issue for React has been that if you reorder stateful nodes, they may lose their state and reload. The thing moving loses its state. There's no way to solve this in general where two stateful nodes swap. The [`moveBefore()` proposal](https://chromestatus.com/feature/5135990159835136?gate=5177450351558656) has now moved to [intent-to-ship](https://groups.google.com/a/chromium.org/g/blink-dev/c/YE_xLH6MkRs/m/_7CD0NYMAAAJ). This function is kind of like `insertBefore` but preserves state. There's [a demo here](https://state-preserving-atomic-move.glitch.me/). Ideally we'd port this demo to a fixture so we can try it. Currently this flag is always off - even in experimental. That's because this is still behind a Chrome flag so it's a little early to turn it on even in experimental. So you need a custom build. It's on in RN but only because it doesn't apply there which makes it easier to tell that it's safe to ship once it's on everywhere else. The other reason it's still off is because there's currently a semantic breaking change. `moveBefore()` errors if both nodes are disconnected. That happens if we're inside a completely disconnected React root. That's not usually how you should use React because it means effects can't read layout etc. However, it is currently supported. To handle this we'd have to try/catch the `moveBefore` to handle this case but we hope this semantic will change before it ships. Before we turn this on in experimental we either have to wait for the implementation to not error in the disconnected-disconnected case in Chrome or we'd have to add try/catch.
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.