Andrew Clark cb1ff430e8 Phased dispatcher (#14701)
* Move DEV-only function right above where it's used

I don't like looking at this top-level function #petty

* Use different dispatchers for functions & classes

Classes support readContext, but not any of the other dispatcher
methods. Function support all methods.

This is a more robust version of our previous strategy of checking
whether `currentlyRenderingFiber` is null.

As a next step, we can use a separate dispatcher for each phase of the
render cycle (mount versus update).

* Use separate dispatchers for mount and update

* Remove mount code from update path

Deletes mount-specific code from the update path, since it should be
unreachable. To continue supporting progressive enhancement (mounting
new hooks at the end of the list), we detect when there are no more
current hooks and switch back to the mount dispatcher. Progressive
enhancement isn't officially supported yet, so it will continue to warn.

* Factoring nits

* Fix Flow

Had to cheat more than I would like

* More Flow nits

* Switch back to using a special dispatcher for nested hooks in DEV

In order for this strategy to work, I had to revert progressive
enhancement support (appending hooks to the end). It was previously a
warning but now it results in an error. We'll reconsider later.

* Always pass args to updateState and updateReducer

Even though the extra args are only used on mount, to ensure
type consistency.
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React · GitHub license npm version Coverage Status CircleCI Status PRs Welcome

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:

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:

class HelloMessage extends React.Component {
  render() {
    return <div>Hello {this.props.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 to evolve 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.

Languages
JavaScript 67.1%
TypeScript 29.4%
HTML 1.5%
CSS 1.1%
C++ 0.6%
Other 0.2%