#[wasm_bindgen]
extern "C" {
    #[wasm_bindgen(js_namespace = console)]
    fn log(msg: &str);
}

macro_rules! log {
    ($($t:tt)*) => (log(&format!($($t)*)))
}

// Called by our JS entry point to run the example.
#[wasm_bindgen]
pub fn run() -> Result<(), JsValue> {
// etc