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One thing that can suspend is the downloading of the RSC stream itself. This tracks an I/O entry for each Promise (`SomeChunk<T>`) that represents the request to the RSC stream. As the value we use the `Response` for `createFromFetch` (or the `ReadableStream` for `createFromReadableStream`). The start time is when you called those. Since we're not awaiting the whole stream, each I/O entry represents the part of the stream up until it got unblocked. However, in a production environment with TLS packets and buffering in practice the chunks received by the client isn't exactly at the boundary of each row. It's a bit longer into larger chunks. From testing, it seems like multiples of 16kb or 64kb uncompressed are common. To simulate a production environment we group into roughly 64kb chunks if they happen in rapid sequence. Note that this might be too small to give a good idea because of the throttle many boundaries might be skipped anyway so this might show too many. The React DevTools will see each I/O entry as separate but dedupe if an outer boundary already depends on the same chunk. This deduping makes it so that small boundaries that are blocked on the same chunk, don't get treated as having unique suspenders. If you have a boundary with large content, then that content will likely be in a separate chunk which is not in the parent and then it gets marked as. This is all just an approximation. The goal of this is just to highlight that very large boundaries will very likely suspend even if they don't suspend on any I/O on the server. In practice, these boundaries can float around a lot and it's really any Suspense boundary that might suspend but some are more likely than others which this is meant to highlight. It also just lets you inspect how many bytes needs to be transferred before you can show a particular part of the content, to give you an idea that it's not just I/O on the server that might suspend. If you don't use the debug channel it can be misleading since the data in development mode stream will have a lot more data in it which leads to more chunking. Similarly to "client references" these I/O infos don't have an "env" since it's the client that has the I/O and so those are excluded from flushing in the Server performance tracks. Note that currently the same Response can appear many times in the same Instance of SuspenseNode in DevTools when there are multiple chunks. In a follow up I'll show only the last one per Response at any given level. Note that when a separate debugChannel is used it has its own I/O entry that's on the `_debugInfo` for the debug chunks in that channel. However, if everything works correctly these should never leak into the DevTools UI since they should never be propagated from a debug chunk to the values waited by the runtime. This is easy to break though.
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.