| # Receiving JavaScript Closures in Exported Rust Functions |
| |
| You can use the `js-sys` crate to access JavaScript's `Function` type, and |
| invoke that function via `Function.prototype.apply` and |
| `Function.prototype.call`. |
| |
| For example, we can wrap a `Vec<u32>` in a new type, export it to JavaScript, |
| and invoke a JavaScript closure on each member of the `Vec`: |
| |
| ```rust |
| use wasm_bindgen::prelude::*; |
| |
| #[wasm_bindgen] |
| pub struct VecU32 { |
| xs: Vec<u32>, |
| } |
| |
| #[wasm_bindgen] |
| impl VecU32 { |
| pub fn each(&self, f: &js_sys::Function) { |
| let this = JsValue::null(); |
| for &x in &self.xs { |
| let x = JsValue::from(x); |
| let _ = f.call1(&this, &x); |
| } |
| } |
| } |
| ``` |
| |
| Since Rust has no function overloading, the `call#` method also requires a |
| number representing the amount of arguments passed to the JavaScript closure. |
