js-sandbox

js-sandbox is a Rust library for executing JavaScript code from Rust in a secure sandbox. It is based on the [Deno] project and uses [serde_json] for serialization.

This library's primary focus is embedding JS as a scripting language into Rust. It does not provide all possible integrations between the two languages, and is not tailored to JS's biggest domain as a client/server side language of the web.

Instead, js-sandbox focuses on calling standalone JS code from Rust, and tries to remain as simple as possible in doing so. The typical use case is a core Rust application that integrates with scripts from external users, for example a plugin system or a game that runs external mods.

This library is in early development, with a basic but powerful API. The API may still evolve considerably.

Examples

Print from JavaScript

The Hello World example -- print something using JavaScript -- is one line, as it should be: rust fn main() { js_sandbox::eval_json("console.log('Hello Rust from JS')").expect("JS runs"); }

Call a JS function

A very basic application calls a JavaScript function triple() from Rust. It passes an argument and accepts a return value, both serialized via JSON:

```rust use js_sandbox::{Script, ErrBox};

fn main() -> Result<(), ErrBox> { let jscode = "function triple(a) { return 3 * a; }"; let mut script = Script::fromstring(js_code)?;

let arg = 7;
let result: i32 = script.call("triple", &arg)?;

assert_eq!(result, 21);
Ok(())

} ```

An example that serializes a JSON object (Rust -> JS) and formats a string (JS -> Rust):

```rust use js_sandbox::{Script, ErrBox}; use serde::Serialize;

[derive(Serialize, PartialEq)]

struct Person { name: String, age: u8, }

fn main() -> Result<(), ErrBox> { let src = r#" function toString(person) { return "A person named " + person.name + " of age " + person.age; }"#;

let mut script = Script::from_string(src)
    .expect("Initialization succeeds");

let person = Person { name: "Roger".to_string(), age: 42 };
let result: String = script.call("toString", &person).unwrap();

assert_eq!(result, "A person named Roger of age 42");
Ok(())

} ```

Maintain state in JavaScript

It is possible to initialize a stateful JS script, and then use functions to modify that state over time. This example appends a string in two calls, and then gets the result in a third call:

```rust use js_sandbox::{Script, ErrBox};

fn main() -> Result<(), ErrBox> { let src = r#" var total = ''; function append(str) { total += str; } function get() { return total; }"#;

let mut script = Script::from_string(src)
    .expect("Initialization succeeds");

let _: () = script.call("append", &"hello").unwrap();
let _: () = script.call("append", &" world").unwrap();
let result: String = script.call("get", &()).unwrap();

assert_eq!(result, "hello world");
Ok(())

} ```