making-webassembly-better-for-rust-3.rs

// Rust
#[wasm_bindgen]
pub struct Foo {
    contents: u32,
}

#[wasm_bindgen]
impl Foo {
    pub fn new() -> Foo {
        Foo { contents: 0 }
    }

making-webassembly-better-for-rust-4.rs

    pub fn add(&mut self, amt: u32) -> u32 {
        self.contents += amt;
        return self.contents
    }
}

making-webassembly-better-for-rust-5.js

// JS
import { Foo } from "./js_hello_world";

making-webassembly-better-for-rust-6.js

let foo = Foo.new();
assertEq(foo.add(10), 10);
foo.free();