解決 mongoose DeprecationWarning 錯誤導致數據庫連接不成功

mongoose 版本低提示錯誤為：

DeprecationWarning: collection.ensureIndex is deprecated. Use createIndexes instead.

通常升級 mongoose 就可以解決：

npm install mongoose

 

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連接數據庫參數缺失提示錯誤：

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.

通常根據錯誤信息提示，將 useNewUrlparser 添加到 mongoose.connect 即可：

// db
const db = "mongodb://localhost:27017/blog";
mongoose.Promise = global.Promise
mongoose.connect(db, { useNewUrlParser: true }).then(() => console.log('Database Successful！')).catch((err) => console.log(err));