express中怎么通过mongoskin连接mongodb，我的老报错[Error: invalid schema, expected mongodb]

E:\nodejs\myapp>npm ls mongodb myapp@0.0.0 E:\nodejs\myapp └── mongodb@2.0.55 extraneous

npm ERR! extraneous: mongodb@2.0.55 E:\nodejs\myapp\node_modules\mongodb

E:\nodejs\myapp>npm ls mongoskin myapp@0.0.0 E:\nodejs\myapp └── mongoskin@2.0.3 extraneous

npm ERR! extraneous: mongoskin@2.0.3 E:\nodejs\myapp\node_modules\mongoskin

E:\nodejs\myapp>npm ls jade myapp@0.0.0 E:\nodejs\myapp └── jade@1.11.0