Check your mongo
version:
mongo --version
If you are using version >= 3.1.0, change your mongo
connection file to ->
MongoClient.connect("mongodb://localhost:27017/YourDB", { useNewUrlParser: true })
or your mongoose connection file to ->
mongoose.connect("mongodb://localhost:27017/YourDB", { useNewUrlParser: true });
Ideally, it's a version 4 feature, but v3.1.0 and above are supporting it too. Check out MongoDB GitHub for details.