oxc/README.md

<p align="center">
  <img alt="OXC Logo" src="https://cdn.jsdelivr.net/gh/oxc-project/oxc-assets/preview-universal.png" width="700">
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[![MIT licensed][license-badge]][license-url]
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## ⚓ Oxc

The Oxidation Compiler is creating a collection of high-performance tools for JavaScript and TypeScript.

Oxc is building a parser, linter, formatter, transformer, minifier, resolver ... all written in Rust.

See more at [oxc.rs](https://oxc.rs)!

## 🙋Who's using Oxc?

- [Rolldown] uses the [oxc][docs-oxc-url] crate for parsing and transformation.
- [Nova engine](https://trynova.dev) uses the [oxc][docs-oxc-url] crate for parsing.
- [Rolldown][rolldown], [Biome][biome], [swc-node](https://github.com/swc-project/swc-node) and [Mako][mako] uses the [oxc_resolver][docs-resolver-url] crate for module resolution.
- Projects and companies like [Preact](https://github.com/preactjs/preact/blob/4c20c23c16dd60f380ce9fe98afc93041a7e1562/oxlint.json), [Shopify](https://oxc.rs/blog/2023-12-12-announcing-oxlint.html#_50-100-times-faster-than-eslint), ByteDance and Shopee uses oxlint for linting.
- ...[and many more](https://oxc.rs/docs/guide/projects.html)

## ⚡️ Linter Quick Start

The linter is ready to catch mistakes for you. It comes with 93 rules turned on by default (out of 430+ in total) and no configuration is required.

To get started, run [oxlint][npm-oxlint] or via `npx`:

```bash
npx oxlint@latest
```

To give you an idea of its capabilities, here is an example from the [vscode] repository, which finishes linting 4800+ files in 0.7 seconds.

<p float="left" align="left">
  <img src="https://cdn.jsdelivr.net/gh/oxc-project/oxc-assets/linter-screenshot.png" width="60%">
</p>

## ⚡️ Performance

- The parser aims to be the fastest Rust-based ready-for-production parser.
- The linter is more than 50 times faster than [ESLint], and scales with the number of CPU cores.

<p float="left" align="middle">
  <img src="https://raw.githubusercontent.com/Boshen/bench-javascript-parser-written-in-rust/main/bar-graph.svg" width="49%">
  <img src="https://raw.githubusercontent.com/Boshen/bench-javascript-linter/main/bar-graph.svg" width="49%">
</p>

## ⌨️ Rust, Node.js and Wasm Usage

### Rust

Individual crates are published, you may use them to build your own JavaScript tools.

- The umbrella crate [oxc][docs-oxc-url] exports all public crates from this repository.
- The AST and parser crates [oxc_ast][docs-ast-url] and [oxc_parser][docs-parser-url] are production ready.
- The resolver crate [oxc_resolver][docs-resolver-url] for module resolution is also production ready.
- Example usages of these crates can be found in their respective `crates/*/examples` directory.

While Rust has gained a reputation for its comparatively slower compilation speed,
we have dedicated significant effort to fine-tune the Rust compilation speed.
Our aim is to minimize any impact on your development workflow,
ensuring that developing your own Oxc based tools remains a smooth and efficient experience.

This is demonstrated by our [CI runs](https://github.com/oxc-project/oxc/actions/workflows/ci.yml?query=branch%3Amain),
where warm runs complete in 3 minutes.

### Node.js

- via napi: [oxc-parser][npm-napi-parser], [oxc-transform][npm-napi-transform]

### Wasm

- [@oxc-parser/wasm](https://www.npmjs.com/package/@oxc-parser/wasm)

---

## 🎯 Tools

- [AST and Parser](#-ast-and-parser)
- [Linter](#-linter)
- [Resolver](#-resolver)
- [Minifier](#-minifier)
- [Formatter](#-formatter)
- [Transformer](#-transformer)

### 🔸 AST and Parser

Oxc maintains its own AST and parser, which is by far the fastest and most conformant JavaScript and TypeScript (including JSX and TSX) parser written in Rust.

As the parser often represents a key performance bottleneck in JavaScript tooling,
any minor improvements can have a cascading effect on our downstream tools.
By developing our parser, we have the opportunity to explore and implement well-researched performance techniques.

While many existing JavaScript tools rely on [estree] as their AST specification,
a notable drawback is its abundance of ambiguous nodes.
This ambiguity often leads to confusion during development with [estree].

The Oxc AST differs slightly from the [estree] AST by removing ambiguous nodes and introducing distinct types.
For example, instead of using a generic [estree] `Identifier`,
the Oxc AST provides specific types such as `BindingIdentifier`, `IdentifierReference`, and `IdentifierName`.
This clear distinction greatly enhances the development experience by aligning more closely with the ECMAScript specification.

#### 🏆 Parser Performance

Our [benchmark][parser-benchmark] reveals that the Oxc parser surpasses the speed of the [swc] parser by approximately 3 times and the [Biome][biome] parser by 5 times.

<details>
  <summary>How is it so fast?</summary>
  <ul>
    <li>AST is allocated in a memory arena (<a href="https://crates.io/crates/bumpalo">bumpalo</a>) for fast AST memory allocation and deallocation.</li>
    <li>Short strings are inlined by <a href="https://crates.io/crates/compact_str">CompactString</a>.</li>
    <li>No other heap allocations are done except the above two.</li>
    <li>Scope binding, symbol resolution and some syntax errors are not done in the parser, they are delegated to the semantic analyzer.</li>
  </ul>
</details>

### 🔸 Linter

The linter embraces convention over configuration, eliminating the need for extensive configuration and plugin setup.
Unlike other linters like [ESLint], which often require intricate configurations and plugin installations (e.g. [@typescript-eslint]),
our linter only requires a single command that you can immediately run on your codebase:

```bash
npx oxlint@latest
```

#### 🏆 Linter Performance

The linter is 50 - 100 times faster than [ESLint] depending on the number of rules and number of CPU cores used.
It completes in less than a second for most codebases with a few hundred files and completes in a few seconds for
larger monorepos. See [bench-javascript-linter](https://github.com/Boshen/bench-javascript-linter) for details.

As an upside, the binary is approximately 5MB, whereas [ESLint] and its associated plugin dependencies can easily exceed 100.

You may also download the linter binary from the [latest release tag](https://github.com/oxc-project/oxc/releases/latest) as a standalone binary,
this lets you run the linter without a Node.js installation in your CI.

<details>
  <summary>How is it so fast?</summary>
  <ul>
    <li>Oxc parser is used.</li>
    <li>AST visit is a fast operation due to linear memory scan from the memory arena.</li>
    <li>Files are linted in a multi-threaded environment, so scales with the total number of CPU cores.</li>
    <li>Every single lint rule is tuned for performance.</li>
  </ul>
</details>

### 🔸 Resolver

Module resolution plays a crucial role in JavaScript tooling, especially for tasks like multi-file analysis or bundling. However, it can often become a performance bottleneck.
To address this, we developed [oxc_resolver][docs-resolver-url].

The resolver is production-ready and is currently being used in [Rolldown][rolldown]. Usage and examples can be found in its own [repository](https://github.com/oxc-project/oxc_resolver).

### 🔸 Transformer

A transformer is responsible for turning higher versions of ECMAScript to a lower version that can be used in older browsers.

TypeScript and React transforms are complete. See [Milestone 2](https://github.com/oxc-project/oxc/issues/2859) for current goals.

[oxc-transform][npm-napi-transform] can be used for experimentation.

### 🔸 Isolated Declarations

[TypeScript Isolated Declarations Emit](https://devblogs.microsoft.com/typescript/announcing-typescript-5-5-beta/#isolated-declarations) without using the TypeScript compiler.

Our [benchmark](https://github.com/oxc-project/bench-transformer) indications that our implementation is at least 20 times faster than the TypeScript compiler.

The [npm package](https://www.npmjs.com/package/oxc-transform) or [crate](https://crates.io/crates/oxc_isolated_declarations) can be used for this task.

### 🔸 Minifier

JavaScript minification plays a crucial role in optimizing website performance as it reduces the amount of data sent to users,
resulting in faster page loads.
This holds tremendous economic value, particularly for e-commerce websites, where every second can equate to millions of dollars.

However, existing minifiers typically require a trade-off between compression quality and speed.
You have to choose between the slowest for the best compression or the fastest for less compression.
But what if we could develop a faster minifier without compromising on compression?

We are actively working on a prototype that aims to achieve this goal,
by porting all test cases from well-known minifiers such as [google-closure-compiler], [terser], [esbuild], and [tdewolff-minify].

Preliminary results indicate that we are on track to achieve our objectives.
With the Oxc minifier, you can expect faster minification times without sacrificing compression quality.

### 🔸 Formatter

While [prettier] has established itself as the de facto code formatter for JavaScript, there is a significant demand in the developer community for a less opinionated alternative. Recognizing this need, our ambition is to undertake research and development to create a new JavaScript formatter that offers increased flexibility and customization options.

The [prototype](https://github.com/oxc-project/oxc/tree/main/crates/oxc_prettier) is currently work in progress.

---

## 🧪Test Infrastructure

In Oxc, correctness and reliability are taken extremely seriously.

We spend half of our time on strengthening the test infrastructure to prevent problems from propagating to downstream tools.

[Test Infrastructure](https://oxc.rs/docs/learn/architecture/test.html) documents our test procedures:

- Conformance suite on Test262, Babel, TypeScript
- Lots of fuzzing
- Linter snapshot diagnostics
- oxlint ecosystem ci
- Idempotency testing
- Code coverage
- End to end 3000 top npm packages

---

## ✍️ Contribute

See [CONTRIBUTING.md](./CONTRIBUTING.md) for guidance.

Check out some of the [good first issues](https://github.com/oxc-project/oxc/contribute) or ask us on [Discord][discord-url].

If you are unable to contribute by code, you can still participate by:

- Add a [GitHub Star](https://github.com/oxc-project/oxc/stargazers) to the project.
- Join us on [Discord][discord-url].
- [Follow me on twitter](https://twitter.com/boshen_c) and tweet about this project.

## 📚 Learning Resources

- My small tutorial on [how to write a JavaScript Parser in Rust](https://oxc.rs/docs/learn/parser_in_rust/intro.html)
- My small article [Pursuit of Performance on Building a JavaScript Compiler](https://oxc.rs/docs/learn/performance.html)
- [And more](https://oxc.rs/docs/learn/references.html)

## 🤝 Credits

This project was incubated with the assistance of these exceptional mentors and their projects:

- [Biome][biome] - [@ematipico](https://github.com/ematipico)
- [Ruff][ruff] - [@charliermarsh](https://github.com/charliermarsh), [@MichaReiser](https://github.com/MichaReiser)
- [quick-lint-js](https://github.com/quick-lint/quick-lint-js) - [@strager](https://github.com/strager)
- [elm-review](https://package.elm-lang.org/packages/jfmengels/elm-review/latest) - [@jfmengels](https://github.com/jfmengels)

Special thanks go to

- [@domonji](https://github.com/domonji) for bootstrapping this project together, and also completing the TypeScript parser.
- [@tongtong-lu](https://github.com/tongtong-lu) and [@guan-wy](https://github.com/guan-wy) for designing the [project logo](https://github.com/oxc-project/oxc-assets).

## ❤ Who's [Sponsoring Oxc](https://github.com/sponsors/Boshen)?

<p align="center">
  <a href="https://github.com/sponsors/Boshen">
    <img src="https://raw.githubusercontent.com/Boshen/sponsors/main/sponsors.svg" alt="My sponsors" />
  </a>
</p>

## 📖 License

Oxc is free and open-source software licensed under the [MIT License](./LICENSE).

Oxc ports or copies code from other open source projects, their licenses are listed in [**Third-party library licenses**](./THIRD-PARTY-LICENSE).

[discord-badge]: https://img.shields.io/discord/1079625926024900739?logo=discord&label=Discord
[discord-url]: https://discord.gg/9uXCAwqQZW
[license-badge]: https://img.shields.io/badge/license-MIT-blue.svg
[license-url]: https://github.com/oxc-project/oxc/blob/main/LICENSE
[ci-badge]: https://github.com/oxc-project/oxc/actions/workflows/ci.yml/badge.svg?event=push&branch=main
[ci-url]: https://github.com/oxc-project/oxc/actions/workflows/ci.yml?query=event%3Apush+branch%3Amain
[npm-badge]: https://img.shields.io/npm/v/oxlint/latest?color=brightgreen
[npm-url]: https://www.npmjs.com/package/oxlint/v/latest
[code-size-badge]: https://img.shields.io/github/languages/code-size/oxc-project/oxc
[code-size-url]: https://github.com/oxc-project/oxc
[code-coverage-badge]: https://codecov.io/github/oxc-project/oxc/branch/main/graph/badge.svg
[code-coverage-url]: https://codecov.io/gh/oxc-project/oxc
[sponsors-badge]: https://img.shields.io/github/sponsors/Boshen
[sponsors-url]: https://github.com/sponsors/Boshen
[playground-badge]: https://img.shields.io/badge/Playground-blue?color=9BE4E0
[playground-url]: https://playground.oxc.rs/
[website-badge]: https://img.shields.io/badge/Website-blue
[website-url]: https://oxc.rs
[crate-oxc-url]: https://crates.io/crates/oxc
[crate-ast-url]: https://crates.io/crates/oxc_ast
[crate-parser-url]: https://crates.io/crates/oxc_parser
[docs-oxc-url]: https://docs.rs/oxc
[docs-ast-url]: https://docs.rs/oxc_ast
[docs-parser-url]: https://docs.rs/oxc_parser
[docs-resolver-url]: https://docs.rs/oxc_resolver
[Boshen]: https://github.com/boshen
[CompactString]: https://github.com/ParkMyCar/compact_str
[ESLint]: https://eslint.org/
[acorn]: https://github.com/acornjs/acorn
[babel]: https://babel.dev
[bumpalo]: https://docs.rs/bumpalo
[contributors]: https://github.com/oxc-project/oxc/graphs/contributors
[enhanced-resolve]: https://github.com/webpack/enhanced-resolve
[esbuild]: https://esbuild.github.io/
[eslint-plugin-import]: https://www.npmjs.com/package/eslint-plugin-import
[eslint-plugin-jest]: https://www.npmjs.com/package/eslint-plugin-jest
[estree]: https://github.com/estree/estree
[google-closure-compiler]: https://github.com/google/closure-compiler
[minification-benchmarks]: https://github.com/privatenumber/minification-benchmarks
[npm-napi-parser]: https://www.npmjs.com/package/oxc-parser
[npm-napi-transform]: https://www.npmjs.com/package/oxc-transform
[npm-oxlint]: https://www.npmjs.com/package/oxlint
[parser-benchmark]: https://github.com/Boshen/bench-javascript-parser-written-in-rust
[prettier]: https://prettier.io
[biome]: https://biomejs.dev/
[ruff]: https://beta.ruff.rs
[swc]: https://swc.rs
[tdewolff-minify]: https://github.com/tdewolff/minify
[terser]: https://terser.org
[vscode]: https://github.com/microsoft/vscode
[@typescript-eslint]: https://typescript-eslint.io
[rolldown]: https://rolldown.rs
[mako]: https://makojs.dev