Andrew Clark
49595e921d
When an async update expires, React renders at the expiration time that corresponds to the current time, not at the original update's expiration time. That way, all the expired work in the tree is flushed in a single batch. This is implemented inside `renderRoot` by comparing the next render expiration time to the current time. If the current time is later, `renderRoot` will restart at the later time. Because of poor factoring, the check is currently performed right before entering the work loop. But the work loop is usually entered multiple times in a single callback: each time a component throws or suspends. This led to an infinite loop where React would detect that an update expired, restart at the current time, make a bit of progress, suspend, check for expired work again, and start the loop again. I fixed this by moving the expired work check to the beginning of `renderRoot`, so that it is not performed every time something suspends. This isn't ideal, because you could technically still fall into a loop if more than 10ms lapse in between exiting `renderRoot` and entering it again. The proper fix is to lift the check outside of `renderRoot` entirely so that the function can restart without checking for expired work again. Since this is exceedingly unlikely (and this whole thing is still behind a flag), I'll do the better fix in an already-planned follow up to fork `renderRoot` into separate functions for sync and async work.
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.
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 Online Playgrounds to get a taste of React.
- Add React to a Website as a
<script>tag in one minute. - Create a New React App if you're looking for a powerful JavaScript toolchain.
You can use React as a <script> tag from a CDN, or as a react package on npm.
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:
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:
function HelloMessage({ name }) {
return <div>Hello {name}</div>;
}
ReactDOM.render(
<HelloMessage name="Taylor" />,
document.getElementById('container')
);
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. If you're using React as a <script> tag, read this section on integrating JSX; otherwise, the recommended JavaScript toolchains handle it automatically.
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.