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_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_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.

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
  A UTF-16–encoded, reference counted, immutable string.
• symbol
  Boa’s implementation of ECMAScript’s global Symbol object.
• value
  Boa’s ECMAScript Value implementation.
• vm
  Boa’s ECMAScript Virtual Machine

Macros

• js_string
  Utility macro to create a JsString.

Structs

• Context
  ECMAScript context. It is the primary way to interact with the runtime.
• JsBigInt
  JavaScript bigint primitive rust type.
• JsError
  The error type returned by all operations related to the execution of Javascript code.
• JsNativeError
  Native representation of an ideal Error object from Javascript.
• JsObject
  Garbage collected Object.
• JsString
  A UTF-16–encoded, reference counted, immutable string.
• JsSymbol
  This represents a JavaScript symbol primitive.
• Module
  ECMAScript’s Abstract module record.
• NativeFunction
  A callable Rust function that can be invoked by the engine.
• Script
  ECMAScript’s Script Record.
• Source
  A source of ECMAScript code.

Enums

• JsNativeErrorKind
  The list of possible error types a JsNativeError can be.
• JsValue
  A Javascript value

Traits

• JsArgs
  A utility trait to make working with function arguments easier.

Type Aliases

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