I was creating a database storing user information. Previously, the system worked well, after I performed npm update of mongoose, the system failed and I dont know why. The following is the error message I encountered.

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

Then, I write some simple testing code to test if the database is connected successfully. For example:

User.findOne({firstName: "David"}, function(err, user){console.log(user.lastName)});

The above worked perfectly.

I then found the corresponding Id from the database directly and create variable like:

var testId = "abcde"

and tried the following code:

User.findById(testId, function(err, user){console.log(user.firstName)});

Then it just output the error messages.

I have tried mongoose.Types.ObjectId.isValid('abcde') (abcde is just example) and it returned true. Therefore, I really have no ideas why it did not work...is it a mongoose bug?

Please help if you know the answer, thank you very much!