Javascript class instance in other class functions (nodejs)

Question

I deal with nodejs and i cannot figure out, why i cannot call class instance from another class function. Here is my code. Please help.

var StationDAO = require('./StationDAO.js');
var StationSearchCriteria = require('./StationSearchCriteria.js');
function GasStationService(lat, long, zoom) {
this.latitude = lat;
this.longitude = long;
this.zoom = zoom;
this.zoomToKilometers = 0.009;
/* ......... */
this.minLat = function () {
 return this.latitude - this.zoomToKilometers;
};
this.minLong = function() {
 return this.longitude - this.zoomToKilometers;
};
this.maxLat = function() {
 return this.latitude + this.zoomToKilometers;
};
this.maxLong = function() {
 return this.longitude + this.zoomToKilometers;
};
this.criteria = new StationSearchCriteria(this.minLat(), this.minLong(), this.maxLat(), this.maxLong());
this.conn = new StationDAO(criteria); // why this doesnt work

• ilmirons: Is StationDAO module defined as a single function bound to module.exports?
• TomHonner: It is class accessing to Elastic search DB and it is module.exports
• ilmirons: Is there any async code in StationDAO? (maybe something is not yet initialized when you are invoking it).
• TomHonner: yes, there is one function, but it isnt called.

Answer 1

you are passing criteria which is not defined i assume you wanted to pass this.criteria isntead.

this.criteria = new StationSearchCriteria(this.minLat(), this.minLong(), this.maxLat(), this.maxLong());
this.conn = new StationDAO(this.criteria); //this should work

• Balayesu Chilakalapudi: if ` criteria ` is not defined then how this.criteria is existing ?
• 0x_Anakin: this.criteria is not the same as criteria. I seriously dont understand your comment.
• Balayesu Chilakalapudi: 'this' pointer refers the current object's variable, in the problem statement 'criteria' is a variable which is the instance of StationSearchCriteria class and is already initialized.
• barry-johnson: +1'd this to bring it to zero since I think someone downvoted it not understanding it. Or maybe I am not understanding. I don't know why someone thinks that foo and this.foo would be the same thing.