node.js - 如何使用Node.js解决“找不到模块”错误？(How do I resolve “Cannot find module” error using Node.js?)

Question

After pulling down a module from GitHub and following the instructions to build it, I try pulling it into an existing project using:

(从GitHub提取模块并按照说明进行构建后，我尝试使用以下方法将其拖入现有项目：)

> npm install ../faye

This appears to do the trick:

(这似乎可以解决问题：)

> npm list
/home/dave/src/server
└─┬ [email protected]
  ├── [email protected]
  ├── [email protected]
  └── [email protected]

But Node.js can't find the module:

(但是Node.js找不到模块：)

> node app.js
node.js:201
        throw e; // process.nextTick error, or 'error' event on first tick
              ^
Error: Cannot find module 'faye'
    at Function._resolveFilename (module.js:334:11)
    at Function._load (module.js:279:25)
    at Module.require (module.js:357:17)
    at require (module.js:368:17)
    at Object.<anonymous> (/home/dave/src/server/app.js:2:12)
    at Module._compile (module.js:432:26)
    at Object..js (module.js:450:10)
    at Module.load (module.js:351:31)
    at Function._load (module.js:310:12)
    at Array.0 (module.js:470:10)

I really want to understand what is going on here, but I'm at a bit of a loss as to where to look next.

(我真的很想了解这里发生了什么，但是我对接下来的去向有些困惑。)

Any suggestions?

(有什么建议么？)

  ask by Dave Causey translate from so

Answer 1

Using npm install installs the module into the current directory only (in a subdirectory called node_modules ).

(使用npm install将模块安装到当前目录中（在名为node_modules的子目录中）。)

Is app.js located under home/dave/src/server/ ?

(app.js是否位于home/dave/src/server/ ？)

If not and you want to use the module from any directory, you need to install it globally using npm install -g .

(如果不是，并且您想从任何目录使用该模块，则需要使用npm install -g全局npm install -g 。)

I usually install most packages locally so that they get checked in along with my project code.

(我通常在本地安装大多数软件包，以便它们与我的项目代码一起签入。)

Update (8/2019):

(更新（8/2019）：)

Nowadays you can use package-lock.json file, which is automatically generated when npm modifies your node_modules directory.

(如今，您可以使用package-lock.json文件，该文件在npm修改您的node_modules目录时自动生成。)

Therefore you can leave out checking in packages, because the package-lock.json tracks the exact versions of your node_modules, you're currently using.

(因此，您package-lock.json签入包，因为package-lock.json跟踪您当前正在使用package-lock.json的确切版本。)

To install packages from package-lock.json instead of package.json use the command npm ci .

(要从package-lock.json而不是package.json安装软件包，请使用命令npm ci 。)

Update (3/2016):

(更新（3/2016）：)

I've received a lot of flak for my response, specifically that I check in the packages that my code depends on.

(我收到了很多回应，特别是我签入了我的代码所依赖的软件包。)

A few days ago, somebody unpublished all of their packages ( https://medium.com/@azerbike/i-ve-just-liberated-my-modules-9045c06be67c#.kq9s64clp ) which broke React, Babel, and just about everything else.

(几天前，有人取消发布了所有软件包（ https://medium.com/@azerbike/i-ve-just-liberated-my-modules-9045c06be67c#.kq9s64clp ），这破坏了React，Babel和几乎所有东西其他。)

Hopefully it's clear now that if you have production code, you can't rely on NPM actually maintaining your dependencies for you.

(希望现在很清楚，如果您具有生产代码，则不能依赖NPM来真正为您维护依赖项。)