nodejs和mongodb常見的小錯誤

1.直接使用nodejs會遇到如下問題：

module.js:340
    throw err;
         ^Error: Cannot find module 'mongodb'

解決方式以下：
After trying for some time to install it without success (since I'm new to mongo and node), I was missing the npm link step indeed. So just to summarize, I did this:
npm install mongodb -g
cd /path/to/my/app/folder
npm link mongodb

2.