使用 Node.js 时，如何解决"无法找到模块"错误？

Question

在从GitHub中取出一个模块并按照构建它的说明操作之后，我尝试使用以下方法将它拉到一个现有的项目中：

> npm install ../faye

这似乎起到了作用：

> npm list
/home/dave/src/server
└─┬ faye@0.7.1
  ├── cookiejar@1.3.0
  ├── hiredis@0.1.13
  └── redis@0.7.1

但是Node.js找不到模块了：

> 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)

我真的很想了解这是怎么回事，这让我有点不知所措。有什么建议吗？

Answer 1

Using npm install installs the module into the current directory only (in a subdirectory called node_modules). Is app.js located under 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.

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

Update (3/2016):

I've received a lot of flak for my response, specifically that I check in the packages that my code depends on. A few days ago, somebody unpublished all of their packages (https://medium.com/@azerbike/i-ve-just-liberated-my-modules-9045c06be67c#.kq9s64clp) which broke React, Babel, and just about everything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. Hopefully it's clear now that if you have production code, you can't rely on NPM actually maintaining your dependencies for you.