e07235b980
We can simplify this tracking by not having a separate pending set of logs and the logs tracked per instance and instead we just track the logs per Fiber. This avoids the need to move it back into the pending set after unmounts in case a Fiber is reparented. The main motivation for this is to unify with an upcoming tracking of logs for Server Components. For those it doesn't make sense to move them into a per instance set and because the same Server Component - and its logs - may appear more than once. So no particular instance should steal it. The second part of this change is that instead of looking up the instance from fiber, which requires the fiberToFiberInstanceMap, we instead look up if a component has any new logs when we traverse it in the commit phase. After all for a component to have had a log it must have updated. This is a similar technique to #30897. This technique also works for Server Components without having to maintain a one to many relationship from ComponentInfo to VirtualInstance. So it unifies them. Normally this look up would be fast since the `fiberToComponentsLogs` set would be empty and so doesn't add any significant weight to the commit phase. If there's a ton of logs on many different components then it's not great since it would slow down the commit phase but that's not what we expect to see so in typical usage, this is better. There is an unfortunate consequence though which is that `console.warn/error` in passive effects (i.e. `useEffect`) wouldn't be picked up because currently we traverse the logs in `handleCommitFiberRoot` which is too early. If we moved that to `handlePostCommitFiberRoot` this wouldn't be a problem. In the meantime, I just detect this and do a brute force flush by walking all mounted instances if there's a `console.warn/error` inside a passive effect. If we ever add "owners" to event handlers that are triggered outside the render/commit phases (like `<div onClick={...}>`) and we want to associate error/warnings in those, we'd need a different technique to ensure those get flushed in time.
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.