Brian Vaughn
0e8a5aff3d
DevTools (and its profilers) should not require users to be familiar with React internals. Although the scheduling profiler includes a CPU sample flame graph, it's there for advanced use cases and shouldn't be required to identify common performance issues. This PR proposes adding new marks around component effects. This will enable users to identify components with slow effect create/destroy functions without requiring them to dig through the call stack. (Once #22529 lands, these new marks will also include component stacks, making them more useful still.) For example, here's a profile with a long-running effect. Without this change, it's not clear why the effects phase takes so long. After this change, it's more clear why that the phase is longer because of a specific component. We may consider adding similar marks around render phase hooks like useState, useReducer, useMemo. I avoided doing that in this PR because it would be a pretty pervasive change to the ReactFiberHooks file. Note that this change should have no effect on production bundles since everything is guarded behind a profiling feature flag. Going to tag more people than I normally would for this pR, since it touches both reconciler and DevTools packages. Feel free to ignore though if you don't have strong feelings. Note that although this PR adds new marks to the scheduling profiler, it's done in a way that's backwards compatible for older profiles.
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.