mongodb custom collection / document methods

I'm new to mongodb and was wondering if it's possible to create custom methods on a collection or on a document. Something like this for example : 

getFullname = function(){
   return this.name + " " + this.surname;
}

var user = db.users.findOne({name:"Bob"})
console.log(user.getFullname());

For node.js, you can use Mongoose with its support for defining virtuals as well as static and instance methods on the model (i.e. collection) schemas.

For a case like your full name example, virtuals are a good fit:

var userSchema = new Schema({
    name: String,
    surname: String
});

userSchema.virtual('fullname').get(function() {
    return this.name + ' ' + this.surname;
});

That would let you do things like:

var User = mongoose.model('User', userSchema);

User.findOne({name:"Bob"}, function(err, user) {
    console.log(user.fullname);
});

There are two ways, but you have to use Mongoose. This more than a mongoDB driver, it's an ORM-like framework. You can use Virtuals or methods:

Virtuals:

as @JohnnyHK, use:

UserSchema.virtual('fullName').get(function() {
    return this.name + ' ' + this.surname;
});

This will create a virtual field which will be accessible in the program but NOT saved to the DB/ The virtual also has a method set which will be called when the value is set

UserSchema.virtual('fullName').get(function() {
    return this.name + ' ' + this.surname;
}).set(function(fullName) {
    this.name = fullName.split(' ')[0];
    this.surname = fullName.split(' ')[1];
});

So when you do:

Doe = new User();
Doe.fullName = "John Doe";
Doe.name
// Doe
Doe.surname
// John

Methods

It's the closest things:

UserSchema.methods.getFullname = function(){
   return this.name + " " + this.surname;
}

JohnDoe.getfullName()

With MongoJS

It's the closest thing to the native driver:

db.cursor.prototype.toArray = function(callback) {
    this._apply('toArray', function(doc) {
       doc.getFullName = ...
       callback(doc);
    });

};