prototype.Function is not being exported in node.js

Question

I found this javascript Kalman filter library online and I wanted to use it with my node.js application. As I wanted to include this js file into my node.js application, I tried to export the required functions ( added module.exports as shown below) .

module.exports = {

  KalmanModel : function(){

    function KalmanModel(x_0,P_0,F_k,Q_k){
      this.x_k  = x_0;
      this.P_k  = P_0;
      this.F_k  = F_k;
      this.Q_k  = Q_k;
    }

    KalmanModel.prototype.update =  function(o){
      // code 
    }

    return KalmanModel;
  },

  KalmanObservation : function(){

    function KalmanObservation(z_k,H_k,Q_k){
      this.z_k = z_k;//observation
      this.H_k = H_k;//observation model
      this.R_k = R_k;//observation noise covariance
    }

    return KalmanObservation;
  }
};

But when I try to run the following piece of code

Code:

var kal =require('./kalman');
var observationVal = observationValues;
var x_0 = $V([observationVal[0]]);
var P_0 = $M([[2]]);
var F_k=$M([[1]]);
//process noise
var Q_k=$M([[0]]);
var KM = kal.KalmanModel(x_0,P_0,F_k,Q_k);
//value we measure
var z_k = $V([observationVal[0]]);
var H_k = $M([[1]]);
var R_k = $M([[4.482]]);
var KO = kal.KalmanObservation(z_k,H_k,R_k);

for (var i=1;i<10;i++){
z_k = $V([observationVal[i]]);
KO.z_k=z_k;
KM.update(KO);

I get an error

TypeError: object is not a function.

It looks like method defined with prototype is not getting exported. What am I doing wrong here?

Answer 1

Well if you don't wanna change much in the existing source code you can do this. Don't remove the implicit function call ie : (function(){//code})(); and i think you should be set.

module.exports = {

    KalmanModel : (function(){

        function KalmanModel(x_0,P_0,F_k,Q_k){
          this.x_k  = x_0;
          this.P_k  = P_0;
          this.F_k  = F_k;
          this.Q_k  = Q_k;
        }

        KalmanModel.prototype.update =  function(o){
          // code 
        }

        return KalmanModel;
    })(),

    KalmanObservation : (function(){

        function KalmanObservation(z_k,H_k,Q_k){
          this.z_k = z_k;//observation
          this.H_k = H_k;//observation model
          this.R_k = R_k;//observation noise covariance
        }

        return KalmanObservation;
    })()
};

Or simply append the following in the library kalman.js

module.exports = {
    myKalmanModel : KalmanModel,
    myKalmanObservation : KalmanObservation
}

and access as

var KM = kal.myKalmanModel(x_0,P_0,F_k,Q_k);