How to fix Mongoose deprecation warning about "strictQuery"

Question

When I start build my backend server, I get this deprecation warning, but it's showing that I'm connected to the database.

File server.js

const dotenv = require('dotenv');
const mongoose = require('mongoose');
const app = express();
dotenv.config();

mongoose
  .connect(process.env.MONGODB_URI)
  .then(() => {
    console.log('connected to db');
  })
  .catch((err) => {
    console.log(err.message);
  });

const port = process.env.PORT || 5000;
app.listen(port, () => {
  console.log(`serve at http://localhost:${port}`);
});

File package.json

{
  "name": "backend",
  "version": "1.0.0",
  "description": "backend",
  "main": "server.js",
  "scripts": {
    "start": "node server",
    "dev": "nodemon server"
  },
  "keywords": [],
  "author": "",
  "license": "ISC",
  "dependencies": {
    "dotenv": "^16.0.3",
    "express": "^4.18.2",
    "mongoose": "^6.8.0"
  },
  "devDependencies": {
    "nodemon": "^2.0.20"
  }
}

And this is the Mongoose deprecation warning:

Screenshot of Mongoose Deprecation Warning

It shows:

[MONGOOSE] DeprecationWarning: Mongoose: the `strictQuery` option will be switched back to `false` by default in Mongoose 7. 
Use `mongoose.set('strictQuery', false);` if you want to prepare for this change. 
Or use `mongoose.set('strictQuery', true);` to suppress this warning.
(Use `node --trace-deprecation ...` to show where the warning was created)

Answer 1

This warning was introduced to notify users about the change that will be introduced in Mongoose 7 to the default value of strictQuery.
It's default value will be brought back to false.

You can either set the strictQuery option to true globally to suppress the warning with:

const dotenv = require('dotenv');
const mongoose = require('mongoose');
const app = express();
dotenv.config();

mongoose.set('strictQuery', true);

Or, set the flag to false if you want to override the current strictQuery behavior and prepare for the new release:

const dotenv = require('dotenv');
const mongoose = require('mongoose');
const app = express();
dotenv.config();

mongoose.set('strictQuery', false);

Either way the warning should disappear.

For more information on why strictQuery will be brought back to false by default see here.
For more information on strictQuery see here.

Answer 2

Add mongoose.set('strictQuery', false); before connecting to the MongoDB server.

mongoose.set('strictQuery', false);
  const conn = await mongoose.connect(process.env.MONGO_URI, {
  useNewUrlParser: true,
 useUnifiedTopology: true,
});