How to properly handle error on mongoose CRUD - node.js

Question

I am building a very simple RESTFUL app to see how Node and Mongo work together.
A made a function to find a "Persona" document on a mongodb by Id, so here is the code:
function getPersonabyId(req,res)
{
//en params del objeto request esta lo que llega por get
let idPersona=req.params.id;
//mongoose trae un método para pillar por id
Persona.findById(idPersona).exec((err,objPersona)=>
{
if(err)
{
res.status(500).send(err);
}
else{
res.status(200).send(objPersona);
}
})
}
And I use this route, where function is executed:
miniApp.get("/getPersonaById/:id",controladorPersona.getPersonabyId);
So, when I pass as parameter a valid ID, everything is ok, I get the proper Persona object in the response.
But when I use a not valid ID (no document with that ID exists on the mongodb), the error specified on the exec callback is thrown... but, isn´t supossed that this error should be thrown only in case there are server problems? a non existent ID should not be a 500 error, isn´t it?
I looked for info and I found this:
https://coursework.vschool.io/mongoose-crud/
Person.find((err, people) => {
// Note that this error doesn't mean nothing was found,
// it means the database had an error while searching, hence the 500 status
if (err) return res.status(500).send(err)
// send the list of all people
return res.status(200).send(people);
});
And reading the commented lines on the code above, confuses me even more... the error, as said in those comments, should be an error database or something similar, not a "not found" error... but the error is actually thrown when an object with that ID is not found!
This is the error I get with a non valid ID:
{
"message": "Cast to ObjectId failed for value \"5b105ba453401c41d0e3da2\" at path \"_id\" for model \"Persona\"",
"name": "CastError",
"stringValue": "\"5b105ba453401c41d0e3da2\"",
"kind": "ObjectId",
"value": "5b105ba453401c41d0e3da2",
"path": "_id"
}

Answer 1

As you are using mongoose, you can validate that the incoming value is an objectId or not by using mongoose.Types.ObjectId.isValid(req.params.id). This will return a boolean and possibly save you some effort or writing the regex for object Id validation.

Answer 2

You have defined your _id as ObjectId in schema. Not every string is a valid ObjectId. the id tha you are passing to findById is not valid. Object id should be 24 characters long string. Add this check before querying,
if (id.match(/^[0-9a-fA-F]{24}$/)) {
// Yes, it's a valid ObjectId, proceed with `findById` call.
} else{
//throw an error
}
or if you want to keep using any string as _id, define _id as String instead of ObjectId in your schema.