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[compiler] Represent array accesses with PropertyLoad (#32287)
Prior to this PR, our HIR represented property access with numeric
literals (e.g. `myVar[0]`) as ComputedLoads. This means that they were
subject to some deopts (most notably, not being easily dedupable /
hoistable as dependencies).

Now, `PropertyLoad`, `PropertyStore`, etc reference numeric and string
literals (although not yet string literals that aren't valid babel
identifiers). The difference between PropertyLoad and ComputedLoad is
fuzzy now (maybe we should rename these).
- PropertyLoad: property keys are string and numeric literals, only when
the string literals are valid babel identifiers
- ComputedLoad: non-valid babel identifier string literals (rare) and
other non-literal expressions

The biggest feature from this PR is that it trivially enables
array-indicing expressions as dependencies. The compiler can also
specify global and imported types for arrays (e.g. return value of
`useState`)


I'm happy to close this if it complicates more than it helps --
alternative options are to entirely rely on instruction reordering-based
approaches like ReactiveGraphIR or make dependency-specific parsing +
hoisting logic more robust.
2025-02-18 11:54:20 -07:00
.codesandbox Codesandbox: upgrade to Node.js 18 (#26330) 2023-03-06 15:38:03 -05:00
.github refactor(eslint-plugin-react-hooks): change array type and improve conditionals (#32400) 2025-02-16 20:28:12 -05:00
compiler [compiler] Represent array accesses with PropertyLoad (#32287) 2025-02-18 11:54:20 -07:00
fixtures ci: add workflow for running the eslint plugin e2e tests (#32397) 2025-02-16 17:00:43 -05:00
packages [flags] enable owner stacks everywhere (#32376) 2025-02-18 10:29:40 -05:00
scripts [flags] enable owner stacks everywhere (#32376) 2025-02-18 10:29:40 -05:00
.editorconfig Remove trim_trailing_whitespace from editorconfig (#31413) 2024-11-04 15:30:02 -05:00
.eslintignore Fix ESLint and Prettier configs for React Compiler (#29073) 2024-05-15 14:02:57 -07:00
.eslintrc.js refactor(eslint-plugin-react-hooks): change array type and improve conditionals (#32400) 2025-02-16 20:28:12 -05:00
.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 feat[devtools]: add package for fusebox integration (#28553) 2024-04-12 15:29:35 +01:00
.mailmap updates mailmap entries (#19824) 2020-09-12 13:05:52 -04:00
.nvmrc [ci] Standardize node version and timezones 2024-07-12 12:53:05 -04:00
.prettierignore [prettier] Ignore compiler/target (#31168) 2024-10-10 10:53:27 -04:00
.prettierrc.js [BE] switch to hermes parser for prettier (#30421) 2024-07-22 19:16:13 -04:00
.watchmanconfig .watchmanconfig must be valid json (#16118) 2019-07-11 19:01:02 -07:00
babel.config-ts.js build: add support to the rollup build for building typescript packages (#32393) 2025-02-16 10:38:13 -05:00
babel.config.js Upgrade tests to use react/jsx-runtime (#28252) 2024-02-05 23:07:41 -05:00
CHANGELOG-canary.md Add useActionState to CHANGELOG-canary.md (#28632) 2024-03-26 13:15:08 -04:00
CHANGELOG.md Fix headings in React 19 CHANGELOG (#31683) 2024-12-06 16:55:53 +01:00
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
LICENSE [Codemod] Update copyright header to Meta (#25315) 2022-10-18 11:19:24 -04:00
MAINTAINERS Update MAINTAINERS (#32238) 2025-01-27 13:40:45 -06:00
netlify.toml [UMD] Remove umd builds (#28735) 2024-04-17 11:15:27 -07:00
package.json refactor(eslint-plugin-react-hooks): change array type and improve conditionals (#32400) 2025-02-16 20:28:12 -05:00
react.code-workspace created a vscode workspace file for the repo (#29830) 2024-06-13 16:23:42 +01:00
ReactVersions.js Fix canary version strings (#31721) 2024-12-12 14:11:24 -05:00
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 refactor(eslint-plugin-react-hooks): change array type and improve conditionals (#32400) 2025-02-16 20:28:12 -05:00

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.