431bb0bddb
We currently only track the reason something might suspend in development mode through debug info but this excludes some cases. As a result we can end up with boundary that suspends but has no cause. This tries to detect that and show a notice for why that might be. I'm also trying to make it work with old React versions to cover everything. In production we don't track any of this meta data like `_debugInfo`, `_debugThenable` etc. so after resolution there's no information to take from. Except suspensey images / css which we can track in prod too. We could track lazy component types already. We'd have to add something that tracks after the fact if something used a lazy child, child as a promise, hooks, etc. which doesn't exist today. So that's not backwards compatible and might add some perf/memory cost. However, another strategy is also to try to replay the components after the fact which could be backwards compatible. That's tricky for child position since there's so many rules for how to do that which would have to be replicated. If you're in development you get a different error. Given that we've added instrumentation very recently. If you're on an older development version of React, then you get a different error. Unfortunately I think my feature test is not quite perfect because it's tricky to test for the instrumentation I just added. https://github.com/facebook/react/pull/34146 So I think for some prereleases that has `_debugOwner` but doesn't have that you'll get a misleading error. Finally, if you're in a modern development environment, the only reason we should have any gaps is because of throw-a-Promise. This will highlight it as missing. We can detect that something threw if a Suspense boundary commits with a RetryCache but since it's a WeakSet we can't look into it to see anything about what it might have been. I don't plan on doing anything to improve this since it would only apply to new versions of React anyway and it's just inherently flawed. So just deprecate it #34032. Note that nothing in here can detect that we suspended Transition. So throwing at the root or in an update won't show that anywhere.
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.