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0.3.0 Jan 2, 2024
0.2.1 Nov 13, 2023
0.1.4 Nov 3, 2023
0.1.3 Oct 25, 2023

#5 in #webidl

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Rust 2K SLoC // 0.0% comments JavaScript 360 SLoC // 0.1% comments

Effortless JS Integration for Rust

Crates.io Build Status License

This crate is meant to provide a quick and simple way to integrate a runtime javacript or typescript component from within rust.

  • By default, the code being run is entirely sandboxed from the host, having no filesystem or network access.
    • It can be extended to include those capabilities and more if desired - please see the 'web' feature, and the runtime_extensions example
  • Asynchronous JS code is supported (I suggest using the timeout option when creating your runtime)
  • Loaded JS modules can import other modules
  • Typescript is supported by default, and will be transpiled into JS for execution

Here is a very basic use of this crate to execute a JS module. It will:

  • Create a basic runtime
  • Load a javascript module,
  • Call a function registered as the entrypoint
  • Return the resulting value
use rustyscript::{json_args, Runtime, Module, Error};

let module = Module::new(
        (string, integer) => {
            console.log(`Hello world: string=${string}, integer=${integer}`);
            return 2;

let value: usize = Runtime::execute_module(
    &module, vec![],
    json_args!("test", 5)

assert_eq!(value, 2);

Modules can also be loaded from the filesystem with Module::load or Module::load_dir if you want to collect all modules in a given directory.

If all you need is the result of a single javascript expression, you can use:

let result: i64 = rustyscript::evaluate("5 + 5").expect("The expression was invalid!");

Or to just import a single module for use:

use rustyscript::{json_args, import};
let mut module = import("js/my_module.js").expect("Something went wrong!");
let value: String = module.call("exported_function_name", json_args!()).expect("Could not get a value!");

There are a few other utilities included, such as rustyscript::validate and rustyscript::resolve_path

A more detailed version of the crate's usage can be seen below, which breaks down the steps instead of using the one-liner Runtime::execute_module:

use rustyscript::{json_args, Runtime, RuntimeOptions, Module, Error, Undefined};
use std::time::Duration;

let module = Module::new(
    let internalValue = 0;
    export const load = (value) => internalValue = value;
    export const getValue = () => internalValue;

// Create a new runtime
let mut runtime = Runtime::new(RuntimeOptions {
    timeout: Duration::from_millis(50), // Stop execution by force after 50ms
    default_entrypoint: Some("load".to_string()), // Run this as the entrypoint function if none is registered

// The handle returned is used to get exported functions and values from that module.
// We then call the entrypoint function, but do not need a return value.
//Load can be called multiple times, and modules can import other loaded modules
// Using `import './filename.js'`
let module_handle = runtime.load_module(&module)?;
runtime.call_entrypoint::<Undefined>(&module_handle, json_args!(2))?;

// Functions don't need to be the entrypoint to be callable!
let internal_value: i64 = runtime.call_function(&module_handle, "getValue", json_args!())?;

Rust functions can also be registered to be called from javascript:

use rustyscript::{ Runtime, Module, serde_json::Value };

let module = Module::new("test.js", " rustyscript.functions.foo(); ");
let mut runtime = Runtime::new(Default::default())?;
runtime.register_function("foo", |args, _state| {
    if let Some(value) = args.get(0) {
        println!("called with: {}", value);

For better performance calling rust code, consider using an extension instead - see the runtime_extensions example for details

The 'state' parameter can be used to persist data - please see the call_rust_from_js example for details

Utility Functions

These functions provide simple one-liner access to common features of this crate:

  • evaluate; Evaluate a single JS expression and return the resulting value
  • import; Get a handle to a JS module from which you can get exported values and functions
  • resolve_path; Resolve a relative path to the current working dir
  • validate; Validate the syntax of a JS expression

Crate features

The table below lists the available features for this crate. Features marked at Preserves Sandbox: NO break isolation between loaded JS modules and the host system. Use with caution.

Please note that the web feature will also enable fs_import and url_import, allowing arbitrary filesystem and network access for import statements

Feature Description Preserves Sandbox Dependencies
console Provides console.* functionality from JS yes deno_console
crypto Provides crypto.* functionality from JS yes deno_crypto, deno_webidl
url Provides the URL, and URLPattern APIs from within JS yes deno_webidl, deno_url
web Provides the Event, TextEncoder, TextDecoder, File, Web Cryptography, and fetch APIs from within JS NO deno_webidl, deno_web, deno_crypto, deno_fetch, deno_url
default Provides only those extensions that preserve sandboxing yes deno_console, deno_crypto, deno_webidl, deno_url
no_extensions Disables all extensions to the JS runtime - you can still add your own extensions in this mode yes None
all Provides all available functionality NO deno_console, deno_webidl, deno_web, deno_crypto, deno_fetch, deno_url
fs_import Enables importing arbitrary code from the filesystem through JS NO None
url_import Enables importing arbitrary code from network locations through JS NO reqwest

Please also check out @Bromeon/js_sandbox, another great crate in this niche

For an example of this crate in use, please check out lavendeux-parser


~2M SLoC