Allow hiding schema fields when calling toJSON

This is a feature request to allow hiding of a schema field when converting the document into json. I’m not sure if it would be better if this was set from inside the schema declaration or from the toJSON call, e.g.

user = new Schema
  username: 
    type: String
  password:
    type: String
    expose: false

or something like

User.findOne({username: 'joe'}, function(err, doc) {
  user = doc.toJSON(hide: 'password')
});

[KuzminDima]

  UserSchema.method('toJSON', function() {
    var user = this.toObject();
    delete user.salt;
    delete user.hash;
    delete user.__v;
    return user;
  });

[olalonde]

Has anyone solved this yet? Otherwise I’ll write that functionality when I have time. How about:

schema.set('toJSON', { hide: 'password salt' })

or maybe

var User = new Schema({
   password:                { type: String, toJSON: false }
   , salt:                  { type: String, toJSON: false }
});

There should probably be an option to ignore this, like:

doc.toJSON({showAll: true}); or doc.toJSON({ignoreOptions: true}); or doc.toRawJSON();