Crate boa_engine

Boa’s boa_engine crate implements ECMAScript’s standard library of builtin objects and an ECMAScript context, bytecompiler, and virtual machine for code execution.

Example usage

You can find multiple examples of the usage of Boa in the boa_examples crate. In order to use Boa in your project, you will need to add the boa_engine crate to your Cargo.toml file. You will need to use a Source structure to handle the JavaScript code to execute, and a Context structure to execute the code:

use boa_engine::{Context, Source};

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
match context.eval(Source::from_bytes(js_code)) {
    Ok(res) => {
        println!(
            "{}",
            res.to_string(&mut context).unwrap().to_std_string_escaped()
        );
    }
    Err(e) => {
        // Pretty print the error
        eprintln!("Uncaught {e}");
    }
};

Crate Features

• serde - Enables serialization and deserialization of the AST (Abstract Syntax Tree).
• profiler - Enables profiling with measureme (this is mostly internal).
• intl - Enables boa’s ECMA-402 Internationalization API (Intl object)

About Boa

Boa is an open-source, experimental ECMAScript Engine written in Rust for lexing, parsing and executing ECMAScript/JavaScript. Currently, Boa supports some of the language. More information can be viewed at Boa’s website.

Try out the most recent release with Boa’s live demo playground.

Boa Crates

• boa_cli - Boa’s CLI && REPL implementation
• boa_ast - Boa’s ECMAScript Abstract Syntax Tree.
• boa_engine - Boa’s implementation of ECMAScript builtin objects and execution.
• boa_gc - Boa’s garbage collector.
• boa_icu_provider - Boa’s ICU4X data provider.
• boa_interner - Boa’s string interner.
• boa_macros - Boa’s macros.
• boa_parser - Boa’s lexer and parser.
• boa_profiler - Boa’s code profiler.
• boa_runtime - Boa’s WebAPI features.
• boa_string - Boa’s ECMAScript string implementation.

Re-exports

• pub use crate::bigint::JsBigInt;
• pub use crate::context::Context;
• pub use crate::error::JsError;
• pub use crate::error::JsNativeError;
• pub use crate::error::JsNativeErrorKind;
• pub use crate::module::Module;
• pub use crate::native_function::NativeFunction;
• pub use crate::object::JsData;
• pub use crate::object::JsObject;
• pub use crate::object::NativeObject;
• pub use crate::script::Script;
• pub use crate::symbol::JsSymbol;
• pub use crate::value::JsValue;
• pub use boa_ast as ast;
• pub use boa_gc as gc;
• pub use boa_interner as interner;
• pub use boa_parser as parser;

Modules

• bigint
  Boa’s implementation of ECMAScript’s bigint primitive type.
• builtins
  Boa’s ECMAScript built-in object implementations, e.g. Object, String, Math, Array, etc.
• bytecompiler
  This module contains the bytecode compiler.
• class
  Traits and structs for implementing native classes.
• context
  The ECMAScript context.
• environments
  Boa’s implementation of ECMAScript’s Environment Records.
• error
  Error-related types and conversions.
• job
  Boa’s API to create and customize ECMAScript jobs and job queues.
• module
  Boa’s implementation of the ECMAScript’s module system.
• native_function
  Boa’s wrappers for native Rust functions to be compatible with ECMAScript calls.
• object
  Boa’s representation of a JavaScript object and builtin object wrappers
• optimizer
  Implements optimizations.
• prelude
  A convenience module that re-exports the most commonly-used Boa APIs
• property
  Boa’s implementation of ECMAScript’s Property Descriptor.
• realm
  Boa’s implementation of ECMAScript’s Realm Records
• script
  Boa’s implementation of ECMAScript’s Scripts.
• string
  This module contains the js_string macro and the js_str macro.
• symbol
  Boa’s implementation of ECMAScript’s global Symbol object.
• value
  Boa’s ECMAScript Value implementation.
• vm
  Boa’s ECMAScript Virtual Machine

Macros

• js_str
  Convert a utf8 string literal to a JsString
• js_string
  Utility macro to create a JsString.

Structs

• HostDefined
  This represents a ECMASCript specification [HostDefined] field.
• JsStr
  This is equivalent to Rust’s &str.
• JsString
  A Latin1 or UTF-16–encoded, reference counted, immutable string.
• Source
  A source of ECMAScript code.

Traits

• Finalize
  Substitute for the Drop trait for garbage collected types.
• JsArgs
  A utility trait to make working with function arguments easier.
• Trace
  The Trace trait, which needs to be implemented on garbage-collected objects.
• TryIntoJsResult
  Create a JsResult from a Rust value. This trait is used to convert Rust types to JS types, including JsResult of Rust values and JsValues.

Type Aliases

• JsResult
  The result of a Javascript expression is represented like this so it can succeed (Ok) or fail (Err)

Derive Macros

• Finalize
  Derive the Finalize trait.
• JsData
  Derive the JsData trait.
• Trace
  Derive the Trace trait.