Losing Object information while passing as parameter [closed]

postaja.js

class Postaja {
    constructor (ime, x, y) {
        this.ime = ime;
        this.x = x;
        this.y = y;
    }

    razdalja(destination) {
        return 0.26591231 * Math.sqrt(Math.pow((this.x - destination.x), 2) + Math.pow((this.y - destination.y), 2));
    }
}

module.exports = Postaja

povezava.js:

class Povezava {
    constructor(zacetek, konec) {
        this.A = zacetek;
        this.B = konec;
    }

    razdalja () {
        return 0.26591231 * Math.sqrt(Math.pow((this.A.x - this.B.x), 2) + Math.pow((this.A.y - this.B.y), 2));
    }
}

module.exports = Povezava;

index.js:

import {default as povezava} from './components/povezava.js';
const pov = new povezava(Object.assign(postaja, tockaA), Object.assign(tockaB));

I encountered a problem when passing an object postaja as a prameter to constructor of povezava in index.js. I have already checked that the value of postaja objects is valid. Can anyone help me figure out what the problem is?