UnhandledPromiseRejectionWarning: CastError: Cast to ObjectId failed for value "undefined" at path "_id" for model "User"

node.js mongodb react-native express mongoose

In your API file

Import ObjectID from mongodb package

const { ObjectID } = require('mongodb');

And change findById like below :

const user = await User.findById({id:req.params.id}).select('-passwordHash');

or may be like this :

const user = await User.findById({id:ObjectID(req.params.id)}).select('-passwordHash');