Question

我正在尝试从官方节点api文档运行Async Hooks的测试代码，并且在控制台中收到错误Error: Cannot find module 'async_hooks'。我已经在脚本顶部添加了const async_hooks = require('async_hooks');。这是我的代码：

const async_hooks = require('async_hooks');

// Return the ID of the current execution context.
const eid = async_hooks.executionAsyncId();

// Return the ID of the handle responsible for triggering the callback of the
// current execution scope to call.
const tid = async_hooks.triggerAsyncId();

// Create a new AsyncHook instance. All of these callbacks are optional.
const asyncHook =
    async_hooks.createHook({ init, before, after, destroy, promiseResolve });

// Allow callbacks of this AsyncHook instance to call. This is not an implicit
// action after running the constructor, and must be explicitly run to begin
// executing callbacks.
asyncHook.enable();

// Disable listening for new asynchronous events.
asyncHook.disable();

//
// The following are the callbacks that can be passed to createHook().
//

// init is called during object construction. The resource may not have
// completed construction when this callback runs, therefore all fields of the
// resource referenced by "asyncId" may not have been populated.
function init(asyncId, type, triggerAsyncId, resource) { }

// before is called just before the resource's callback is called. It can be
// called 0-N times for handles (e.g. TCPWrap), and will be called exactly 1
// time for requests (e.g. FSReqWrap).
function before(asyncId) { }

// after is called just after the resource's callback has finished.
function after(asyncId) { }

// destroy is called when an AsyncWrap instance is destroyed.
function destroy(asyncId) { }

// promiseResolve is called only for promise resources, when the
// `resolve` function passed to the `Promise` constructor is invoked
// (either directly or through other means of resolving a promise).
function promiseResolve(asyncId) { }

我很困惑，我需要安装npm install async_hooks，但我认为它是nodeJs内置模块，因此我们只需要在顶部进行安装即可。

Answer 1

经过大量搜索后，我发现我正在使用旧版本的nodejs，并且在Node Version 8.x中首先引入了async_hooks模块。使用nvm（节点版本管理器）升级版本后，问题已解决。您可以通过以下链接安装和管理多个nodejs版本：https://www.digitalocean.com/community/tutorials/how-to-install-node-js-with-nvm-node-version-manager-on-a-vps

如果已经安装了nvm，则可以按以下方式打开版本8.x：

列出所有已安装的版本：

 nvm ls

v4.4.4
->       v4.4.7
         v8.8.0
         system
default -> 4.4.7 (-> v4.4.7)
node -> stable (-> v8.8.0) (default)
stable -> 8.8 (-> v8.8.0) (default)

要打开特定的一个，

nvm use v8.8.0
Now using node v8.8.0 (npm v5.4.2)

错误：在NodeJ中找不到模块'async_hooks'

1 个答案: