This is an experimental Javascript lexer, parser and interpreter written in Rust.
Currently, it has support for some of the language.
[![Build Status][build_badge]][build_link]
[](https://codecov.io/gh/boa-dev/boa)
[](https://crates.io/crates/boa_engine)
[](https://docs.rs/boa_engine)
[](https://discord.gg/tUFFk9Y)
[](https://matrix.to/#/#boa:matrix.org)
[build_badge]: https://github.com/boa-dev/boa/actions/workflows/rust.yml/badge.svg?event=push&branch=main
[build_link]: https://github.com/boa-dev/boa/actions/workflows/rust.yml?query=event%3Apush+branch%3Amain
## Live Demo (WASM)
Try out the engine now at the live WASM playground [here](https://boajs.dev/playground)!
Prefer a CLI? Feel free to try out `boa_cli`!
## Boa Crates
Boa currently publishes and actively maintains the following crates:
- **`boa_ast`** - Boa's ECMAScript Abstract Syntax Tree
- **`boa_cli`** - Boa's CLI && REPL implementation
- **`boa_engine`** - Boa's implementation of ECMAScript builtin objects and
execution
- **`boa_gc`** - Boa's garbage collector
- **`boa_interner`** - Boa's string interner
- **`boa_parser`** - Boa's lexer and parser
- **`boa_profiler`** - Boa's code profiler
- **`boa_icu_provider`** - Boa's ICU4X data provider
- **`boa_runtime`** - Boa's WebAPI features
- **`boa_string`** - Boa's ECMAScript string implementation.
Please note: the `Boa` and `boa_unicode` crates are deprecated.
## Boa Engine Example
To use `Boa` simply follow the below.
Add the below dependency to your `Cargo.toml`:
```toml
[dependencies]
boa_engine = "0.19.0"
```
Then in `main.rs`, copy the below:
```rust
use boa_engine::{Context, Source, JsResult};
fn main() -> JsResult<()> {
let js_code = r#"
let two = 1 + 1;
let definitely_not_four = two + "2";
definitely_not_four
"#;
// Instantiate the execution context
let mut context = Context::default();
// Parse the source code
let result = context.eval(Source::from_bytes(js_code))?;
println!("{}", result.display());
Ok(())
}
```
Now, all that's left to do is `cargo run`.
Congrats! You've executed your first `JavaScript` using `Boa`!
## Documentation
For more information on `Boa`'s API. Feel free to check out our documentation.
[**API Documentation**](https://docs.rs/boa_engine/latest/boa_engine/)
## Conformance
To know how much of the _ECMAScript_ specification does Boa cover, you can check out results
running the _ECMASCript Test262_ test suite [here](https://boajs.dev/conformance).
## Contributing
Please, check the [CONTRIBUTING.md](CONTRIBUTING.md) file to know how to
contribute in the project. You will need Rust installed and an editor. We have
some configurations ready for VSCode.
### Debugging
Check [debugging.md](./docs/debugging.md) for more info on debugging.
### Web Assembly
This interpreter can be exposed to JavaScript!
You can build the example locally with:
```shell
npm run build
```
In the console you can use `window.evaluate` to pass JavaScript in.
To develop on the web assembly side you can run:
```shell
npm run serve
```
then go to `http://localhost:8080`.
## Usage
- Clone this repo.
- Run with `cargo run -- test.js` in the project root directory where `test.js` is a path to an existing JS file with any valid JS code.
- If any JS doesn't work then it's a bug. Please raise an [issue](https://github.com/boa-dev/boa/issues/)!
### Example
## Command-line Options
```txt
Usage: boa [OPTIONS] [FILE]...
Arguments:
[FILE]... The JavaScript file(s) to be evaluated
Options:
--strict Run in strict mode
-a, --dump-ast [] Dump the AST to stdout with the given format [possible values: debug, json, json-pretty]
-t, --trace Dump the AST to stdout with the given format
--vi Use vi mode in the REPL
-O, --optimize
--optimizer-statistics
--flowgraph [] Generate instruction flowgraph. Default is Graphviz [possible values: graphviz, mermaid]
--flowgraph-direction Specifies the direction of the flowgraph. Default is top-top-bottom [possible values: top-to-bottom, bottom-to-top, left-to-right, right-to-left]
--debug-object Inject debugging object `$boa`
-m, --module Treats the input files as modules
-r, --root Root path from where the module resolver will try to load the modules [default: .]
-h, --help Print help (see more with '--help')
-V, --version Print version
```
## Roadmap
See [Milestones](https://github.com/boa-dev/boa/milestones).
## Benchmarks
See [Benchmarks](https://boajs.dev/benchmarks).
## Profiling
See [Profiling](./docs/profiling.md).
## Changelog
See [CHANGELOG.md](./CHANGELOG.md).
## Communication
Feel free to contact us on [Matrix](https://matrix.to/#/#boa:matrix.org) if you have any questions.
Contributor discussions take place on the same Matrix Space if you're interested in contributing.
We also have a [Discord](https://discord.gg/tUFFk9Y) for any questions or issues.
## License
This project is licensed under the [Unlicense](./LICENSE-UNLICENSE) or [MIT](./LICENSE-MIT) licenses, at your option.
