Andrew ClarkandGitHub
723ac64ce7
* Move isActEnvironment check to function that warns I'm about to fork the behavior in legacy roots versus concurrent roots even further, so I'm lifting this up so I only have to fork once. * Lift `mode` check, too Similar to previous commit. I only want to check this once. Not for performance reasons, but so the logic is easier to follow. * Expand act warning to include non-hook APIs In a test environment, React warns if an update isn't wrapped with act — but only if the update originates from a hook API, like useState. We did it this way for backwards compatibility with tests that were written before the act API was introduced. Those tests didn't require act, anyway, because in a legacy root, all tasks are synchronous except for `useEffect`. However, in a concurrent root, nearly every task is asynchronous. Even tasks that are synchronous may spawn additional asynchronous work. So all updates need to be wrapped with act, regardless of whether they originate from a hook, a class, a root, or any other type of component. This commit expands the act warning to include any API that triggers an update. It does not currently account for renders that are caused by a Suspense promise resolving; those are modelled slightly differently from updates. I'll fix that in the next step. I also removed the check for whether an update is batched. It shouldn't matter, because even a batched update can spawn asynchronous work, which needs to be flushed by act. This change only affects concurrent roots. The behavior in legacy roots is the same. * Expand act warning to include Suspense resolutions For the same reason we warn when an update is not wrapped with act, we should warn if a Suspense promise resolution is not wrapped with act. Both "pings" and "retries". Legacy root behavior is unchanged.
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 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 which have a relatively limited scope. This is a great place to get started.
License
React is MIT licensed.