Mongoose mapReduce Error: OUT parameter must be defined

I am using mongoose framework to communicate with the mongodb. Now i am in the situation to join the two collections using mapReduce. I have followed this tutoria "http://blog.knoldus.com/2014/03/12/easiest-way-to-implement-joins-in-mongodb-2-4/" to get it done. I have successfully done with join using mapReduce in mongoDB Shell using robomongo. Same i am trying with mongoose frame work but its giving me error that Out parameter must be defied.

The code sample what i have done.

This is the collection schema for User profile:

  var User = new mongoose.Schema({
       name : {
        first : {type : String},
        last : {type : String}
    },
    title : {type : String},
    userName : {type : String, unique : true},
    profileImgUrl : {type : String},
    mojo : Number
 });

this is the collection schema for the testimonials:

var Testimonials = new mongoose.Schema({
     from : String,
     to : String,
     text : String
  });

This is the code using mongoose, nodejs:-

var mapTalent = function () {
            var output= {userName : this.userName,firstname:this.name.first,                      lastname:this.name.last , profileImgUrl : this.profileImgUrl, mojo : this.mojo, text : null}
                emit(this.userName, output);
            };

var mapTestimonial = function () {
            var output = {fromTalentName : this.fromTalentName, firstname:null, lastname:null, profileImgUrl : null, mojo : null, text : this.text}
                emit(this.text, output);
            };

 var reduceF = function(key, values) {
        var outs = {firstname:null, lastname:null , profileImgUrl:null, text : null, mojo:null};

        values.forEach(function(v){

                       if(outs.firstname ==null){
                            outs.firstname = v.firstname
                        }
                        if(outs.lastname ==null){
                            outs.lastname = v.lastname
                        }
                        if(outs.profileImgUrl ==null){
                            outs.profileImgUrl = v.profileImgUrl
                        }
                        if(outs.mojo ==null){
                            outs.mojo = v.mojo
                        }
                        if(outs.text == null){
                            outs.text = v.text
                        }
         });
        return outs;
    };

  result = Testimonials.mapReduce(mapTestimonial, reduceF, {out : {reduce : "Talent_Testimonials"}});

   result = Talent.mapReduce(mapTalent, reduceF, {out : {reduce : "Talent_Testimonials"}});

Here the error is thrown as " the out option parameter must be defined".

What i am doing wrong here i am not getting. This same works in mongoDB shell.