Saving a model using mongoose

Question

I just started studying the MEAN stack and I am stuck with a very trivial problem. I have created a model using mongoose using the code below:

var mongoose = require('mongoose');
var axisData = mongoose.Schema({ xaxis:String, yaxis:String });
module.exports = mongoose.model('AxisData',axisData);

And i am trying to save the above model using the below code:

var axisDataModel = require('../models/models');

where the "../models/models" is the location where the above defined model is stored.

module.exports.saveAxisData=function(req,res){
    var axisData=new axisDataModel(req.body);
    axisData.save(function(err){
                    if(err)
                         console.log(err);
                     else
                          console.log(todo);
                   });
      };

But unfortunately, the callback inside save() never gets called. Whichever site I referred to, told the same thing. Can anyone help me?