# JavaScriptCore API for Rust

[![crates](https://img.shields.io/crates/v/rusty_jsc.svg)](https://crates.io/crates/rusty_jsc)
[![docs](https://docs.rs/rusty_jsc/badge.svg)](https://docs.rs/rusty_jsc)

This library provides a Rust API for the JavaScriptCore engine with the following goals:

* High-level API like the JavaScriptCore API for Swift
* Wrap the low-level C++ API instead of `jsc` to avoid the dependency to GTK.

## Getting Started

### Implementing a JavaScript runtime

Please check out [PunJS](examples/punjs) for an example of how to implement a JavaScript runtime with `rusty_jsc`.

### Evaluating a JavaScript script
```rust
use rusty_jsc::JSContext;

let mut context = JSContext::default();
let value = context.evaluate_script("'hello, world'", 1);
if let Some(value) = value {
    println!("{}", value.to_string(&context));
    // Prints:
    // hello, world
}
```

### Callbacks from JavaScript to Rust

```rust
use rusty_jsc::{JSContext, JSValue};
use rusty_jsc_macros::callback;

// The JavaScript code calls this Rust function.
#[callback]
fn foo(_context: JSContext) {
    println!("hello from Rust land!");
}

fn main() {
    let mut context = JSContext::default();
    let callback = JSValue::callback(&context, Some(foo));
    let mut global = context.get_global_object();
    global.set_property(&context, "foo".to_string(), callback);
    context.evaluate_script("foo()", 1);
    // Prints:
    // hello from Rust land!
}
```

## FAQ

### What about the other JavaScriptCore bindings for Rust?

The wrappers in `rusty_jsc` are built against `<JavaScriptCore/JavaScript.h>` header rather than the `jsc` variant that requires GTK.

### Why JavaScriptCore when there's already `rusty_v8`?

[Bun](https://bun.sh) has shown that JavaScriptCore is a worthy contender to V8 on the server-side, so let's bring it over to the Rust ecosystem as well.

### How were the C++ low-level bindings generated?

I first used `bindgen` to do the rough conversion of `JavaScript/JavaScript.h` header and then cleaned it up by hand.
The plan is to maintain the low-level bindings by hand.