from_js_ref

Runtime traits for converting between JS-imported reference types and Rust-exported wasm-bindgen types.

This crate is the companion to wasm_refgen, which generates implementations of these traits via a proc-macro.

Traits

FromJsRef

pub trait FromJsRef: Sized {
    type JsRef: JsCast;

    /// Convert from a JS reference type to the Rust type.
    fn from_js_ref(castable: &Self::JsRef) -> Self;

    /// Attempt to convert from a raw `JsValue`.
    ///
    /// Provided by default using `dyn_ref` (instanceof).
    /// `wasm_refgen` overrides this with a duck-type check via
    /// `Reflect::has` for reliable validation.
    fn try_from_js_value(js_value: &JsValue) -> Option<Self> { /* ... */ }
}

JsDeref

A convenience trait blanket-implemented for all T::JsRef types:

let wasm_foo: WasmFoo = js_foo.js_deref();

Usage

You typically don't implement these traits by hand. Instead, use #[wasm_refgen(js_ref = JsFoo)] on your impl block, which generates the FromJsRef implementation automatically.

use from_js_ref::FromJsRef;

// From a typed reference (infallible)
let foo: WasmFoo = WasmFoo::from_js_ref(&js_foo);

// From a raw JsValue (fallible, duck-type validated)
let foo: Option<WasmFoo> = WasmFoo::try_from_js_value(&js_value);

[!WARNING] Do not use dyn_into::<JsFoo>() or dyn_ref::<JsFoo>() with wasm_refgen-generated types. These rely on instanceof, which targets the Rust identifier name rather than the JS class name. Use FromJsRef::try_from_js_value instead.

License

Apache-2.0