MongoDB mongoose Deprecation Warning

Update:

5.2.10 is released and available for download here.

For more info on the docs you can view pagehttps://mongoosejs.com/docs/deprecations

For more info on the issue and its fixhttps://github.com/Automattic/mongoose/issues/6880

Original Answer:

Mongoose 5.2.9 version upgraded the native mongodb driver to 3.1.3 in which changes were added to throw warning messages when the deprecated native driver method is called.

fields option is deprecated and is replaced with projection option.

You will have to wait for mongoose to make changes at their end to replace the fields option with projection. The fix is scheduled for 5.2.10 release.

For time being you can go back to 5.2.8 which will suppress all deprecation warnings.

npm install mongoose@5.2.8

For all other deprecated warnings you have to approach them case by case.

You will see other deprecation warnings when you use other collection methods.

DeprecationWarning: collection.findAndModify is deprecated. Use findOneAndUpdate, findOneAndReplace or findOneAndDelete instead.DeprecationWarning: collection.remove is deprecated. Use deleteOne, deleteMany, or bulkWrite instead.DeprecationWarning: collection.update is deprecated. Use updateOne, updateMany, or bulkWrite instead.DeprecationWarning: collection.save is deprecated. Use insertOne, insertMany, updateOne, or updateMany instead.DeprecationWarning: collection.ensureIndex is deprecated. Use createIndexes instead.

All findOne* mongoose write methods by default use the findAndModify method which is deprecated in mongodb native driver.

Use mongoose.set('useFindAndModify', false); to have mongooose call the appropriate findOne* method on the mongodb native driver.

For remove and update replace those calls with delete* and update* methods respectively.

For save replace those calls with insert*/ update* methods respectively.

Use mongoose.set('useCreateIndex', true); to have mongooose call the createIndex method on the mongodb native driver.

mongoose.connect('your db url', {  useCreateIndex: true,  useNewUrlParser: true})

or

mongoose.set('useCreateIndex', true)mongoose.connect('your db url', { useNewUrlParser: true })

After upgrading to version 5.2.10. Any of the options below can be use

const mongoose = require('mongoose');mongoose.connect('mongodb://localhost/test', {  useCreateIndex: true,  useNewUrlParser: true}).then(() => console.log('connecting to database successful')).catch(err => console.error('could not connect to mongo DB', err));

const mongoose = require('mongoose');mongoose.set('useCreateIndex', true);mongoose.connect('mongodb://localhost/test',{    useNewUrlParser: true}).then(() =>  console.log('connecting to database successful') ).catch(err =>  console.error('could not connect to mongo DB', err) );