cd28a946d5
This implements `observeUsing(observer)` and `unobserverUsing(observer)`
on fragment instances. IntersectionObservers and ResizeObservers can be
passed to observe each host child of the fragment. This is the
equivalent to calling `observer.observe(child)` or
`observer.unobserve(child)` for each child target.
Just like the addEventListener, the observer is held on the fragment
instance and applied to any newly mounted child. So you can do things
like wrap a paginated list in a fragment and have each child
automatically observed as they commit in.
Unlike, the event listeners though, we don't `unobserve` when a child is
removed. If a removed child is currently intersecting, the observer
callback will be called when it is removed with an empty rect. This lets
you track all the currently intersecting elements by setting state from
the observer callback and either adding or removing them from your list
depending on the intersecting state. If you want to track the removal of
items offscreen, you'd have to maintain that state separately and append
intersecting data to it in the observer callback. This is what the
fixture example does.
There could be more convenient ways of managing the state of multiple
child intersections, but basic examples are able to be modeled with the
simple implementation. Let's see how the usage goes as we integrate this
with more advanced loggers and other features.
For now you can only attach one observer to an instance. This could
change based on usage but the fragments are composable and could be
stacked as one way to apply multiple observers to the same elements.
In practice, one pattern we expect to enable is more composable logging
such as
```javascript
function Feed({ items }) {
return (
<ImpressionLogger>
{items.map((item) => (
<FeedItem />
))}
</ImpressionLogger>
);
}
```
where `ImpressionLogger` would set up the IntersectionObserver using a
fragment ref with the required business logic and various components
could layer it wherever the logging is needed. Currently most callsites
use a hook form, which can require wiring up refs through the tree and
merging refs for multiple loggers.
|
||
|---|---|---|
| .codesandbox | ||
| .github | ||
| compiler | ||
| fixtures | ||
| packages | ||
| scripts | ||
| .editorconfig | ||
| .eslintignore | ||
| .eslintrc.js | ||
| .git-blame-ignore-revs | ||
| .gitattributes | ||
| .gitignore | ||
| .mailmap | ||
| .nvmrc | ||
| .prettierignore | ||
| .prettierrc.js | ||
| .watchmanconfig | ||
| babel.config-react-compiler.js | ||
| babel.config-ts.js | ||
| babel.config.js | ||
| CHANGELOG-canary.md | ||
| CHANGELOG.md | ||
| CODE_OF_CONDUCT.md | ||
| CONTRIBUTING.md | ||
| dangerfile.js | ||
| LICENSE | ||
| MAINTAINERS | ||
| package.json | ||
| react.code-workspace | ||
| ReactVersions.js | ||
| README.md | ||
| SECURITY.md | ||
| yarn.lock | ||
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.