boa-dev/boa: Boa is an embeddable Javascript engine written in Rust.

Boa is an experimental JavaScript lexer, parser, and interpreter written in Rust 🦀, supported by More Over 90% of the latest ECMAScript specification. We continually improve conformance to keep up with the ever-evolving standards.

Try the engine now in the live WASM playground here!

Prefer CLI? feel free to try boa_cli,

Boa currently publishes and actively maintains the following crates:

• boa_ast – Boa’s ECMAScript abstract syntax tree
• boa_cli – CLI and REPL implementation of Boa
• boa_engine – Boa’s implementation and execution of ECMAScript created objects
• boa_gc – Boa’s garbage collector
• boa_interner – Boa’s String Interner
• boa_parser – Boa’s lexer and parser
• boa_icu_provider – Boa’s ICU4X data provider
• boa_runtime – Boa’s WebAPI features
• boa_string – Boa’s ECMAScript string implementation.
• tag_ptr – Utility library that enables a pointer to be associated with a tag of some type usize,

Just add this to start using Boa boa_engine crate for you Cargo.toml,

[dependencies]
boa_engine = "0.21.0"

then in main.rsCopy below:

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 have executed your first JavaScript code using Boa!

For more information on the Boa API, feel free to check out our documentation.

API Documentation

To know more information about the compatibility of Boa around single script Specification, you can check our ECMAScript Test262 Test suite results here.

Please, check out the CONTRIBUTING.md file to learn how to contribute to the project. You will need Rust installed and an editor. We have some configurations ready for VSCode.

Check debugging.md for more information on debugging.

• enable js Feature flag.
• set RUSTFLAGS='--cfg getrandom_backend="wasm_js"'

rustflags can also be set by adding .cargo/config.toml File in project root directory:

[target.wasm32-unknown-unknown]
rustflags = '--cfg getrandom_backend="wasm_js"'

For more information see: getrandom WebAssembly support

• Clone this repo.
• run with cargo run -- test.js where in the project root directory test.js is the path to an existing JS file with any valid JS code.
• If any JS doesn’t work it’s a bug. Please raise an issue!

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

View milestones.

The current benchmarks are taken from the benchmarks for v8 which you can find here. You can also see the results of a nightly benchmark run comparing Boa with other JavaScript engines here.

If you want to run the benchmark locally, run Boa in Release combined.js Script that includes all sub-benchmarks bench-v8 Directory.

cargo run --release -p boa_cli -- bench-v8/combined.js

View profiling.

See CHANGELOG.md.

If you have any questions please feel free to contact us at Matrix. Contributor discussions take place on the same Matrix space if you’re interested in contributing. We also have discord for any question or issue.

This project is licensed under the Unlicensed or the MIT License, at your option.