http://mongoosejs.com/docs/populate.html

http://*.com/questions/6578178/node-js-mongoose-js-string-to-objectid-function

在mongoose里面使用引用对象（id，ref）

http://api.mongodb.org/java/2.0/org/bson/types/ObjectId.html

MongoDB中BSON.TYPES.OBJECTID

http://mongoosejs.com/docs/schematypes.html

Mongoose中的SchemaTypes

http://docs.mongodb.org/manual/reference/object-id/

MongoDB中的ObjectId机器getTimestanp

http://*.com/questions/17595377/json-schema-regarding-use-of-ref

json schema regarding use of ref

http://mongoosejs.com/docs/guide.html#id

option里面的id默认打开或者关闭

http://mongoosejs.com/docs/api.html#schematype_SchemaType

Mongoose的SchemaType