How to export a variable which is in a class in Nodejs

Question

This is my file loginHandler.js

class LoginHandler {
 merchantId = '';
    returnURLForIframe(req, res) {
      merchantId = req.params.merchantId;
    }  
}

module.exports = new LoginHandler();

I want to access the variable merchantId on another file

const loginHandler  = require('./loginHandler')
class ResponseHandler {
    
    getResponseFromCOMM(options,token, res){
        console.log(loginHandler.merchantId)
    }
}

But merchantId is undefined. Can you please tell me what I am doing wrong?

Here you can see the code on Glitch = https://glitch.com/edit/#!/turquoise-spiky-chrysanthemum

It works on my side, you can try as well `console.log(loginHandler)` to see the full object — malarres, Aug 24 '20 at 10:13
It is because your merchantId is an empty string. Try with something like ```merchantId= 'default'``` — Karlan, Aug 24 '20 at 10:16
But it's value is set inside the function returnURLForIframe — Nehal Jaisalmeria, Aug 24 '20 at 10:22
No, it is not set now, because you are using an instance of a class you need to change your code to ```this.merchantId = req.params.merchantId``` — Karlan, Aug 24 '20 at 10:35
@Karlan If I do that, I get this error `Error is TypeError: Cannot set property 'merchantId' of undefined ` — Nehal Jaisalmeria, Aug 24 '20 at 10:38
I don't know the context of your code but it works for me. See my answer. — Karlan, Aug 24 '20 at 10:47
@Karlan `req.params` have nothing to do with this class. @NehalJaisalmeria your need to instantiate the class using the `new` keyword. — Konrad, Aug 24 '20 at 11:02
I've seen @Karlan's answer and it's ok, but this comment with `req.params` was wrong, — Konrad, Aug 24 '20 at 11:09
@NehalJaisalmeria Can you paste the full error when you do `console.log(loginHandler)`? — malarres, Aug 24 '20 at 11:09
@malarres `Error is ReferenceError: merchantId is not defined at returnURLForIframe (C:\Users\Acer\angularProjects\pamSetup\comm-channel-node-gateway\handler\loginHandler.js:8:18) ` — Nehal Jaisalmeria, Aug 24 '20 at 11:23
`const express = require('express'), router = express.Router()` `router.get('^/:userId/:userType/:sessId/:lang/:orgId/:merchantId/:domainId', loginHandler.returnURLForIframe)` — Nehal Jaisalmeria, Aug 24 '20 at 11:32
After adding `this` I'm getting `Error is TypeError: Cannot set property 'merchantId' of undefined at returnURLForIframe (C:\Users\Acer\angularProjects\pamSetup\comm-channel-node-gateway\handler\loginHandler.js:10:23` — Nehal Jaisalmeria, Aug 24 '20 at 11:35

score 2 · Accepted Answer · answered Aug 25 '20 at 11:50

2

I solved it by adding it to an environment variable on loginHandler.js

process.env.MERCHANT_ID = req.params.merchantId

and then on responseHandler.js, I accessed that variable

merchantId : process.env.MERCHANT_ID

answered Aug 25 '20 at 11:50

Nehal Jaisalmeria

414
7
22

score 1 · Answer 2 · answered Aug 24 '20 at 10:46

1

My loginhanderler.js

class LoginHandler {
  merchantId = '';
  returnURLForIframe(req, res) {
    this.merchantId = req.params.merchantId;
  }
}

module.exports = new LoginHandler();

My index.js

let loginHandler = require('./loginhandler');

let req = {
  params: {
    merchantId: 'a test',
  },
};

loginHandler.returnURLForIframe(req);

console.log(loginHandler.merchantId);

answered Aug 24 '20 at 10:46

Karlan

353
1
2
10

I have edited the question. Please check second file – Nehal Jaisalmeria Aug 24 '20 at 11:15

score 0 · Answer 3 · answered Aug 24 '20 at 11:18

0

You can define it as an object key

class LoginHandler {
  constructor() {
    this.merchantId = '';     
  }

    returnURLForIframe(req, res) {
      this.merchantId = req.params.merchantId;
    }  
}

answered Aug 24 '20 at 11:18

Sarath P S

131
5

malarres · Answer 4 · 2020-08-24T11:37:24.087

0

new LoginHandler

class LoginHandler {
    merchantId = "";
  returnURLForIframe(req, res) {
    this.merchantId = req.params.merchantId;
  }
}

module.exports = new LoginHandler();

FOR FUTURE REFERENCE (also for myself)

It was confusing to detect what the error was, so for me it was helpful to change the name of the variable:

class LoginHandler {
    other= "";
  returnURLForIframe(req, res) {
    other = req.params.merchantId;
  }
}

module.exports = new LoginHandler();

Then I saw that the error was ReferenceError: other is not defined and could solve it.

Also, besides logging, it was needed to call returnURLForIframe to see the error

const loginHandler = require("./loginHandler");
class ResponseHandler {
  getResponseFromCOMM(options, token, res) {
    loginHandler.returnURLForIframe({ params: { merchantId: "lalala" } });
    console.log(loginHandler);
  }
}
let rh = new ResponseHandler();
rh.getResponseFromCOMM("foo", "bar", "baz");

edited Aug 24 '20 at 11:37

answered Aug 24 '20 at 11:32

malarres

2,941
1
21
35

I updated it with `this.merchantId = req.params.merchantId;` But I'm getting `Error is TypeError: Cannot set property 'merchantId' of undefined at returnURLForIframe (C:\Users\Acer\angularProjects\pamSetup\comm-channel-node-gateway\handler\loginHandler.js:10:23)` – Nehal Jaisalmeria Aug 24 '20 at 11:37
@NehalJaisalmeria this can be related to how you call the function. `loginHandler.returnURLForIframe({ params: { merchantId: "lalala" } });` will work – malarres Aug 24 '20 at 11:38
https://glitch.com/edit/#!/turquoise-spiky-chrysanthemum check this on Glitch. – Nehal Jaisalmeria Aug 24 '20 at 12:05
Maybe that's another question to ask ;-) Also because you'll have the opportunity to tag `expressJS` and get experts on the matter – malarres Aug 24 '20 at 12:16
I got this error .. `Error is TypeError: loginHandler.returnURLForIframe is not a function at ResponseHandler.getResponseFromCOMM ` Please help me out. Not able to figure the issue. I just want to export the `merchantId` from `loginHandler.js` to `responseHandler.js` – Nehal Jaisalmeria Aug 24 '20 at 16:05

How to export a variable which is in a class in Nodejs

4 Answers4

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