Resolve the Error “casterror: cast to objectid failed for value”

JavaScript is an amazing programming language for creating interactive website pages and applications that leave a remarkable impact on users all over the world. JavaScript provides ease of designing various projects just the way programmers want. It is still in demand as programmers are using it for web pages, and there are infinite websites all with JavaScript elements. So, it is a worldwide accepted and most used programming language. It has many frameworks and libraries that are created for the convenience of the programmer. Programming has become simpler when used with libraries. Node.js is a JavaScript runtime environment that is most frequently used. While mongoose is an object-oriented JavaScript library, which is known to create a connection between Node.js and MongoDB.

When you are working with node, you may encounter various errors, and “casterror: cast to objectid failed for value” is one of those. Don’t worry when this error pops up as we have solutions that can easily fix the error quickly. Let’s check out how the error occurs

How the error shows up

When you are working with node and mongoose to create a path in order to create a child object by adding it to the parent’s array, you land up in trouble. This is the error you get when the string ID is passed into findByID:

TypeError: Object {} has no method 'cast'

You get the following error when trying to pass an ObjectId:

CastError: Cast to ObjectId failed for value "[object Object]" at path "_id"

Another error that shows up is:

error: CastError: Cast to ObjectId failed for value "[object Object]" at path "_id" {"path":"51c35e5ced18cb901d000001","instance":"ObjectID","validators":[],"setters":[],"getters":[],"_index":null}

You end up with the error warning when you run the following code:

var mongoose = require('mongoose');
var Schema = mongoose.Schema;
var ObjectId = Schema.ObjectId; //Have also tried Schema.Types.ObjectId, mongoose.ObjectId

mongoose.connect('mongodb://user:password@server:port/database');

app.get('/myClass/:Id/childClass/create', function(request, result) {
  var id = new ObjectId(request.params.Id);
  MyClass.findById(id).exec( function(err, myClass) {
    if (err || !myClass) { result.send("error: " + err + "<br>" + JSON.stringify(id) || ("object '" + request.params.Id + "' not found: " + id)); return; }
    var child = ChildClass();
    myClass.Children.addToSet(child);
    myClass.save();
    result.send(child);
  });
});

Solutions To Fix the Error “casterror: cast to objectid failed for value”

Solution 1 – Use the correct ID format

The main cause of the error is the field _id you used to filter is not in the correct ID format. See the example that makes the error appears

const mongoose = require('mongoose');

console.log(mongoose.Types.ObjectId.isValid('53cb6b9b4f4ddef1ad47f943'));
// true
console.log(mongoose.Types.ObjectId.isValid('whatever'));
// false

In order to fix the error warning, you need to make sure the value of the search criterion is a valid ObjectId. Have a look at the below code to resolve the error

const criteria = {};
criteria.$or = [];

if(params.q) {
  if(mongoose.Types.ObjectId.isValid(params.id)) {
    criteria.$or.push({ _id: params.q })
  }
  criteria.$or.push({ name: { $regex: params.q, $options: 'i' }})
  criteria.$or.push({ email: { $regex: params.q, $options: 'i' }})
  criteria.$or.push({ password: { $regex: params.q, $options: 'i' }})
}

return UserModule.find(criteria).exec(() => {
  // do stuff
})

Solution 2 – Use mongoose.Types.ObjectId

In mongoose, strings are well-accepted for object ids and properly cast them. The code you can use is:

MyClass.findById(req.params.id)

In the case req.params.id is an invalid format for an ID string of Mongo, you get the exception that you need to catch. You may get confused to understand that mongoose.SchemaTypes is used when you define the schema for mongoose. While you can only utilize mongoose.Types at the time of creating data object to store in either query objects or database.  You can get the exception an invalid ID string is given.

A query object is being taken by ‘findOne’ that also passes a module to the callback. While ‘fineOne({_id: id}) works as a wrapper for ‘fineById’. Further, ‘find’ is used to take a query object as well as pass an array of the matching model to the callback.

Start a bit slow because mongoose needs a bit of practice to keep working with it. Moreover, not using ‘new’ when you are using childclass in your code you get the error message.

Conclusion

In this post, we discussed the ways to resolve the error “casterror: cast to objectid failed for value”. I hope you find it helpful!

I wish you luck!