CommonJS 模块中的类方法不可访问？

Question

我正在为Chapter 11 of the Eloquent Javascript book 的“跟踪手术刀”练习寻找解决方案。本书为章节相关代码提供了CommonJS模块：crow-tech.js

以下是我目前的解决方案代码：

const ct = require('./crow-tech');

function storage(nest, name) {
  return new Promise(resolve => {
    nest.readStorage(name, result => resolve(result));
  });
}

async function locateScalpel(nest) {
    let place = await storage(nest, 'scalpel');
    if (place === nest.name) {
        return place;
    } else if (place !== null) {
        return await locateScalpel(place);
    } else {
        return null;
    }
}

function locateScalpel2(nest) {
  // Your code here.
}

locateScalpel(ct.bigOak).then(console.log);
// → Butcher Shop

这里ct.bigOak 是类Node 的对象，其中包含方法readStorage。在使用console.log 进行的隔离测试中，我可以看到ct.bigOak 被正确导入并且ct.bigOak.readStorage 是一个函数。但是，当我在 Node 中运行上述代码时，会收到以下错误消息：

(node:5441) UnhandledPromiseRejectionWarning: TypeError: nest.readStorage is not a function
    at resolve (/home/<username>/programming/js/eloquent-javascript/tracking-the-scalpel.js:5:10)
    at new Promise (<anonymous>)
    at storage (/home/<username>/programming/js/eloquent-javascript/tracking-the-scalpel.js:4:10)
    at locateScalpel (/home/<username>/programming/js/eloquent-javascript/tracking-the-scalpel.js:10:23)
    at locateScalpel (/home/<username>/programming/js/eloquent-javascript/tracking-the-scalpel.js:14:22)
(node:5441) UnhandledPromiseRejectionWarning: Unhandled promise rejection. This error originated either by throwing inside of an async function without a catch block, or by rejecting a promise which was not handled with .catch(). (rejection id: 2)
(node:5441) [DEP0018] DeprecationWarning: Unhandled promise rejections are deprecated. In the future, promise rejections that are not handled will terminate the Node.js process with a non-zero exit code.

将ct.bigOak 传递到我的本地函数中是否存在一些问题，导致readStorage 方法无法被识别？

Answer 1

问题在于第二次调用 locateScalpel，而不是第一次。

locateScalpel(place) - 这里。