nodejs和mongodb常见的小错误

1.直接使用nodejs会遇到以下问题：

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

解决方式如下：
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.