A declarative, efficient, and flexible JavaScript library for building user interfaces. reactjs.org
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Joseph Savona adbc32de32
[compiler] More fbt compatibility (#34887)
In my previous PR I fixed some cases but broke others. So, new approach.
Two phase algorithm:

* First pass is forward data flow to determine all usages of macros.
This is necessary because many of Meta's macros have variants that can
be accessed via properties, eg you can do `macro(...)` but also
`macro.variant(...)`.
* Second pass is backwards data flow to find macro invocations (JSX and
calls) and then merge their operands into the same scope as the macro
call.

Note that this required updating PromoteUsedTemporaries to avoid
promoting macro calls that have interposing instructions between their
creation and usage. Macro calls in general are pure so it should be safe
to reorder them.

In addition, we're now more precise about `<fb:plural>`, `<fbt:param>`,
`fbt.plural()` and `fbt.param()`, which don't actually require all their
arguments to be inlined. The whole point is that the plural/param value
is an arbitrary value (along with a string name). So we no longer
transitively inline the arguments, we just make sure that they don't get
inadvertently promoted to named variables.

One caveat: we actually don't do anything to treat macro functions as
non-mutating, so `fbt.plural()` and friends (function form) may still
sometimes group arguments just due to mutability inference. In a
follow-up, i'll work to infer the types of nested macro functions as
non-mutating.

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[//]: # (BEGIN SAPLING FOOTER)
Stack created with [Sapling](https://sapling-scm.com). Best reviewed
with [ReviewStack](https://reviewstack.dev/facebook/react/pull/34887).
* #34900
* __->__ #34887
2025-10-17 11:37:28 -07:00
.codesandbox Update Code Sandbox CI to Node 20 to Match .nvmrc (#34329) 2025-08-28 18:33:12 -04:00
.github [ci] Dry run with debug mode (#34767) 2025-10-07 15:16:18 -04:00
compiler [compiler] More fbt compatibility (#34887) 2025-10-17 11:37:28 -07:00
fixtures [eprh] Prepare for 7.0.0 (#34757) 2025-10-08 15:17:31 -04:00
flow-typed Update Flow to 0.265 (#34270) 2025-08-22 15:22:22 -04:00
packages [ESLint] Disallow passing effect event down when inlined as a prop (#34820) 2025-10-16 14:18:01 -04:00
scripts Add MIT license header to feature flag utility script (#34833) 2025-10-16 14:20:21 -04:00
.editorconfig Remove trim_trailing_whitespace from editorconfig (#31413) 2024-11-04 15:30:02 -05:00
.eslintignore Update Flow to 0.263 (#34269) 2025-08-22 12:10:13 -04:00
.eslintrc.js Enable rules-of-hooks for DevTools (#34645) 2025-09-29 15:31:06 +02:00
.git-blame-ignore-revs Add run prettier commit to .git-blame-ignore-revs 2024-07-18 17:42:45 -04:00
.gitattributes .gitattributes to ensure LF line endings when we should 2014-01-17 16:25:53 -08:00
.gitignore [DevTools] Don't inline workers for extensions (#34508) 2025-09-17 17:59:55 +02:00
.mailmap updates mailmap entries (#19824) 2020-09-12 13:05:52 -04:00
.nvmrc Upgrade node.js to 20 LTS (#32855) 2025-04-14 12:52:02 -04:00
.prettierignore [prettier] Ignore compiler/target (#31168) 2024-10-10 10:53:27 -04:00
.prettierrc.js [scripts] Switch back to flow parser for prettier (#33414) 2025-06-03 00:00:28 -04:00
.watchmanconfig .watchmanconfig must be valid json (#16118) 2019-07-11 19:01:02 -07:00
babel.config-react-compiler.js feat(eslint-plugin-react-hooks): merge rule from eslint-plugin-react-compiler into react-hooks plugin (#32416) 2025-03-12 21:43:06 -04:00
babel.config-ts.js [compiler] Aggregate error reporting, separate eslint rules (#34176) 2025-08-21 14:53:34 -07:00
babel.config.js Partially revert #32588 (#32621) 2025-03-15 15:21:57 -04:00
CHANGELOG.md Fix changelog link (#34879) 2025-10-16 13:40:26 -04:00
CODE_OF_CONDUCT.md revert last grammatical edit (#25067) 2022-08-10 20:14:31 +01:00
CONTRIBUTING.md Fix: Updated link in CONTRIBUTING (#25381) 2022-10-03 10:29:57 -04:00
dangerfile.js Fix typo in dangerfile.js which results in an unreachable code path… (#32277) 2025-01-31 01:44:02 -05:00
flow-typed.config.json Update Flow to 0.263 (#34269) 2025-08-22 12:10:13 -04:00
LICENSE [Codemod] Update copyright header to Meta (#25315) 2022-10-18 11:19:24 -04:00
MAINTAINERS Update MAINTAINERS (#34534) 2025-09-19 15:49:08 -04:00
package.json Enable rules-of-hooks for DevTools (#34645) 2025-09-29 15:31:06 +02:00
react.code-workspace created a vscode workspace file for the repo (#29830) 2024-06-13 16:23:42 +01:00
ReactVersions.js [eprh] Prepare for 7.0.0 (#34757) 2025-10-08 15:17:31 -04:00
README.md [ez] Remove circleci badge from readme 2024-07-29 13:26:14 -04:00
SECURITY.md Create SECURITY.md (#15784) 2020-01-09 14:07:41 -08:00
yarn.lock [compiler] improve zod v3 backwards compat (#34877) 2025-10-16 09:46:55 -07:00

React · GitHub license npm version (Runtime) Build and Test (Compiler) TypeScript 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 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:

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:

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.