Sebastian Markbåge
9f2eebd807
Stacked on #28849, #28854, #28853. Behind a flag. If you're following along from the side-lines. This is probably not what you think it is. It's NOT a way to get updates to a component over time. The AsyncIterable works like an Iterable already works in React which is how an Array works. I.e. it's a list of children - not the value of a child over time. It also doesn't actually render one component at a time. The way it works is more like awaiting the entire list to become an array and then it shows up. Before that it suspends the parent. To actually get these to display one at a time, you have to opt-in with `<SuspenseList>` to describe how they should appear. That's really the interesting part and that not implemented yet. Additionally, since these are effectively Async Functions and uncached promises, they're not actually fully "supported" on the client yet for the same reason rendering plain Promises and Async Functions aren't. They warn. It's only really useful when paired with RSC that produces instrumented versions of these. Ideally we'd published instrumented helpers to help with map/filter style operations that yield new instrumented AsyncIterables. The way the implementation works basically just relies on unwrapThenable and otherwise works like a plain Iterator. There is one quirk with these that are different than just promises. We ask for a new iterator each time we rerender. This means that upon retry we kick off another iteration which itself might kick off new requests that block iterating further. To solve this and make it actually efficient enough to use on the client we'd need to stash something like a buffer of the previous iteration and maybe iterator on the iterable so that we can continue where we left off or synchronously iterate if we've seen it before. Similar to our `.value` convention on Promises. In Fizz, I had to do a special case because when we render an iterator child we don't actually rerender the parent again like we do in Fiber. However, it's more efficient to just continue on where we left off by reusing the entries from the thenable state from before in that case.
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.