8da0da0937
* Remove distinction between long, short transitions We're removing the `timeoutMs` option, so there's no longer any distinction between "short" and "long" transitions. They're all treated the same. This commit doesn't remove `timeoutMs` yet, only combines the internal priority levels. * Disable `timeoutMs` argument tl;dr ----- - We're removing the `timeoutMs` argument from `useTransition`. - Transitions will either immediately switch to a skeleton/placeholder view (when loading new content) or wait indefinitely until the data resolves (when refreshing stale content). - This commit disables the `timeoutMS` so that the API has the desired semantics. It doesn't yet update the types or migrate all the test callers. I'll do those steps in follow-up PRs. Motivation ---------- Currently, transitions initiated by `startTransition` / `useTransition` accept a `timeoutMs` option. You can use this to control the maximum amount of time that a transition is allowed to delay before we give up and show a placeholder. What we've discovered is that, in practice, every transition falls into one of two categories: a **load** or a **refresh**: - **Loading a new screen**: show the next screen as soon as possible, even if the data hasn't finished loading. Use a skeleton/placeholder UI to show progress. - **Refreshing a screen that's already visible**: keep showing the current screen indefinitely, for as long as it takes to load the fresh data, even if the current data is stale. Use a pending state (and maybe a busy indicator) to show progress. In other words, transitions should either *delay indefinitely* (for a refresh) or they should show a placeholder *instantly* (for a load). There's not much use for transitions that are delayed for a small-but-noticeable amount of time. So, the plan is to remove the `timeoutMs` option. Instead, we'll assign an effective timeout of `0` for loads, and `Infinity` for refreshes. The mechanism for distinguishing a load from a refresh already exists in the current model. If a component suspends, and the nearest Suspense boundary hasn't already mounted, we treat that as a load, because there's nothing on the screen. However, if the nearest boundary is mounted, we treat that as a refresh, since it's already showing content. If you need to fix a transition to be treated as a load instead of a refresh, or vice versa, the solution will involve rearranging the location of your Suspense boundaries. It may also involve adding a key. We're still working on proper documentation for these patterns. In the meantime, please reach out to us if you run into problems that you're unsure how to fix. We will remove `timeoutMs` from `useDeferredValue`, too, and apply the same load versus refresh semantics to the update that spawns the deferred value. Note that there are other types of delays that are not related to transitions; for example, we will still throttle the appearance of nested placeholders (we refer to this as the placeholder "train model"), and we may still apply a Just Noticeable Difference heuristic (JND) in some cases. These aren't going anywhere. (Well, the JND heuristic might but for different reasons than those discussed above.) |
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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.