问题

1. node连接Mongoose时抛出了两个DeprecationWarning(弃用警告)：

(node:61084) DeprecationWarning: current URL string parser is deprecated, and will be removed in a future version. To use the new parser, pass option { useNewUrlParser: true } to MongoClient.connect.
// 弃用警告：当前的URL字符串解析器已弃用，并且在将来的版本中会移除该功能。要用新的解析器，需要在调用MongoClient.connect是传参：{ useNewUrlParser: true }

(node:61084) DeprecationWarning: current Server Discovery and Monitoring engine is deprecated, and will be removed in a future version. To use the new Server Discover and Monitoring engine, pass option { useUnifiedTopology: true } to the MongoClient constructor.
// 弃用警告：当前的Server Discovery和Monitoring engine已弃用，并且在将来的版本中会移除该功能。要用新的Server Discover和Monitoring engine，需要在调用MongoClient.connect是传参：{ useUnifiedTopology: true }

解决

- MongoClient.connect(yourUrl)
+ MongoClient.connect(yourUrl, { useNewUrlParser: true, useUnifiedTopology: true })