Mofei Zhang
db40a5b15f
This validation ensures that React compiler-enabled apps remain correct. That is, code that errors with this validation is most likely ***invalid*** with React compiler is enabled (specifically, hook calls will be compiled to if-else memo blocks).
Hook guards are used extensively for Meta's react compiler rollouts. There, they're enabled for developers (for dev builds) and on e2e test runs. Let's enable by default for oss as well
### Examples of inputs this rule throws on
* Components should not be invoked directly as React Compiler could memoize the call to AnotherComponent, which introduces conditional hook calls in its compiled output.
```js
function Invalid1(props) {
const myJsx = AnotherComponent(props);
return <div> { myJsx } </div>;
}
```
* Hooks must be named as hooks. Similarly, hook calls may not appear in functions that are not components or hooks.
```js
const renamedHook = useState;
function Invalid2() {
const [state, setState] = renamedHook(0);
}
function Invalid3() {
const myFunc = () => useContext(...);
myFunc();
}
```
* Hooks must be directly called (from the body of a component or hook)
```
function call(fn) {
return fn();
}
function Invalid4() {
const result = call(useMyHook);
}
```
### Example of hook guard error (in dev build)
<img width="1237" alt="image" src="https://github.com/user-attachments/assets/e9ada403-b0d7-4840-b6d5-ad600519c6e6" />
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.