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Andrew Clark 696e736be1
Warn if static flag is accidentally cleared (#20807)
* Warn if static flag is accidentally cleared

"Static" fiber flags are flags that are meant to exist for the lifetime
of a component. It's really important not to accidentally reset these,
because we use them to decide whether or not to perform some operation
on a tree (which we can do because they get bubbled via `subtreeFlags)`.

We've had several bugs that were caused by this mistake, so we actually
don't rely on static flags anywhere, yet. But we'd like to.

So let's roll out this warning and see if it fires anywhere. Once we
can confirm that there are no warnings, we can assume that it's safe
to start using static flags.

I did not wrap it behind a feature flag, because it's dev-only, and we
can use our internal warning filter to hide this from the console.

* Intentionally clear static flag to test warning

* ...and fix it again
2021-02-11 14:20:46 -08:00
.circleci CI job to check that forks are in sync (#20795) 2021-02-10 16:09:20 -08:00
.codesandbox Fix codesandbox build command (#20731) 2021-02-04 11:24:07 -05:00
.github Deprecate old test script commands (#19893) 2020-10-14 08:54:34 -04:00
fixtures Always rethrow original error when we replay errors (#20425) 2020-12-10 05:50:41 -08:00
packages Warn if static flag is accidentally cleared (#20807) 2021-02-11 14:20:46 -08:00
scripts Parallelize Flow in CI (#20794) 2021-02-10 17:54:58 -06:00
.editorconfig https link to editorconfig.org (#18421) 2020-03-29 15:18:52 +01:00
.eslintignore Import React Concurrent Mode Profiler (#19634) 2020-08-20 14:06:28 -04:00
.eslintrc.js Land rest of effects refactor in main fork (#20644) 2021-01-22 14:49:33 -05:00
.gitattributes .gitattributes to ensure LF line endings when we should 2014-01-17 16:25:53 -08:00
.gitignore Build stable and experimental with same command (#20573) 2021-01-12 09:32:32 -08:00
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.watchmanconfig .watchmanconfig must be valid json (#16118) 2019-07-11 19:01:02 -07:00
AUTHORS Request to update email (#20533) 2021-02-10 23:34:07 -05:00
CHANGELOG.md 17.0.1 2020-10-22 13:24:46 +01:00
CODE_OF_CONDUCT.md Adopt Contributor Covenant (#16613) 2019-08-29 16:04:47 -07:00
CONTRIBUTING.md [Gatsby] "https://facebook.github.io/react/" -> "https://reactjs.org/" (#10970) 2017-09-29 18:43:22 -07:00
LICENSE Drop the year from Facebook copyright headers and the LICENSE file. (#13593) 2018-09-07 15:11:23 -07:00
README.md Update README.md 2020-07-08 18:30:18 +01:00
SECURITY.md Create SECURITY.md (#15784) 2020-01-09 14:07:41 -08:00
appveyor.yml Revert "Move MS Windows build to CircleCI (#17984)" (#18302) 2020-03-12 20:57:13 -07:00
babel.config.js Babel 7 (#16297) 2019-08-08 17:46:35 -07:00
dangerfile.js sizebot: Combine stable and experimental results (#20753) 2021-02-06 12:57:11 -08:00
netlify.toml add netlify toml file (#12350) 2018-05-20 21:03:51 +01:00
package.json Add command to publish preleases via CI (#20728) 2021-02-03 15:42:34 -08:00
yarn.lock [devtools] Bump electron version from 9.1.0 to 11.1.0 for darwin-arm64 builds (#20496) 2021-01-04 10:38:11 -05:00

README.md

React · GitHub license npm version 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:

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.