Question

Let’s say I have the following schema

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

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

EDIT: If an user trying to update field, that does not exists, I need throw exception. My question is how can I check that an updating field does not exists in the updating document. Here is a little example what I need:

  app.post('/user/update/:id', function (req, res) {
     var field = req.param('field'),
          value = req.param('value'),
          id = req.param('id');

     User.findOne({_id: id},function(err, user){
        if(err) throw err;

        if (user) {

          user[field] = value;          // Here is I need to check that field is exists
                                        // in user schema. If does't I have to throw 
                                        // an execption.

          user.save(function (err){
             return res.send(200);
          });
        }            
     })
  });

Answer 1

Try adding $exists to the query parameter of update(). This will allow you to only update documents if a certain field exists (or not).

http://www.mongodb.org/display/DOCS/Advanced+Queries#AdvancedQueries-%24exists