在导入的方法、getter 和 setter 上大量使用 structural 属性 允许您定义鸭子类型接口。鸭子类型接口是指，许多不同的 JavaScript 对象，它们在原型链中没有相同的基类，因此不是 instanceof 相同的基类，但可以以相同的方式使用。

# #![allow(unused_variables)]
#fn main() {
use wasm_bindgen::prelude::*;

/// Here is a duck-typed interface for any JavaScript object that has a `quack`
/// method.
///
/// Note that any attempts to check if an object is a `Quacks` with
/// `JsCast::is_instance_of` (i.e. the `instanceof` operator) will fail because
/// there is no JS class named `Quacks`.
#[wasm_bindgen]
extern "C" {
    pub type Quacks;

    #[wasm_bindgen(structural, method)]
    pub fn quack(this: &Quacks) -> String;
}

/// Next, we can export a function that takes any object that quacks:
#[wasm_bindgen]
pub fn make_em_quack_to_this(duck: &Quacks) {
    let _s = duck.quack();
    // ...
}

#}

import { make_em_quack_to_this } from "./rust_duck_typed_interfaces";

// All of these objects implement the `Quacks` interface!

const alex = {
  quack: () => "you're not wrong..."
};

const ashley = {
  quack: () => "<corgi.gif>"
};

const nick = {
  quack: () => "rappers I monkey-flip em with the funky rhythm I be kickin"
};

// Get all our ducks in a row and call into wasm!

make_em_quack_to_this(alex);
make_em_quack_to_this(ashley);
make_em_quack_to_this(nick);