b548b3cd64
* Decouple update queue from Fiber type The update queue is in need of a refactor. Recent bugfixes (#12528) have exposed some flaws in how it's modeled. Upcoming features like Suspense and [redacted] also rely on the update queue in ways that weren't anticipated in the original design. Major changes: - Instead of boolean flags for `isReplace` and `isForceUpdate`, updates have a `tag` field (like Fiber). This lowers the cost for adding new types of updates. - Render phase updates are special cased. Updates scheduled during the render phase are dropped if the work-in-progress does not commit. This is used for `getDerivedStateFrom{Props,Catch}`. - `callbackList` has been replaced with a generic effect list. Aside from callbacks, this is also used for `componentDidCatch`. * Remove first class UpdateQueue types and use closures instead I tried to avoid this at first, since we avoid it everywhere else in the Fiber codebase, but since updates are not in a hot path, the trade off with file size seems worth it. * Store captured errors on a separate part of the update queue This way they can be reused independently of updates like getDerivedStateFromProps. This will be important for resuming. * Revert back to storing hasForceUpdate on the update queue Instead of using the effect tag. Ideally, this would be part of the return type of processUpdateQueue. * Rename UpdateQueue effect type back to Callback I don't love this name either, but it's less confusing than UpdateQueue I suppose. Conceptually, this is usually a callback: setState callbacks, componentDidCatch. The only case that feels a bit weird is Timeouts, which use this effect to attach a promise listener. I guess that kinda fits, too. * Call getDerivedStateFromProps every render, even if props did not change Rather than enqueue a new setState updater for every props change, we can skip the update queue entirely and merge the result into state at the end. This makes more sense, since "receiving props" is not an event that should be observed. It's still a bit weird, since eventually we do persist the derived state (in other words, it accumulates). * Store captured effects on separate list from "own" effects (callbacks) For resuming, we need the ability to discard the "own" effects while reusing the captured effects. * Optimize for class components Change `process` and `callback` to match the expected payload types for class components. I had intended for the update queue to be reusable for both class components and a future React API, but we'll likely have to fork anyway. * Only double-invoke render phase lifecycles functions in DEV * Use global state to track currently processing queue in DEV
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 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 own project.
Documentation
You can find the React documentation on the website.
It 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:
class HelloMessage extends React.Component {
render() {
return <div>Hello {this.props.name}</div>;
}
}
ReactDOM.render(
<HelloMessage name="John" />,
document.getElementById('container')
);
This example will render "Hello John" 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. We recommend using Babel with a React preset to convert JSX into native JavaScript for browsers to digest.
Installation
React is available as the react package on npm. It is also available on a CDN.
React is flexible and can be used in a variety of projects. You can create new apps with it, but you can also gradually introduce it into an existing codebase without doing a rewrite.
The recommended way to install React depends on your project. Here you can find short guides for the most common scenarios:
Contributing
The main purpose of this repository is to continue to evolve 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 which have a relatively limited scope. This is a great place to get started.
License
React is MIT licensed.