JavaScript class from C++

derived.js

/**
  This is the C++ example
  
  #include <iostream>
  using namespace std;
  
  class Base 
  {
  public:
    int m_id;
    
    Base(int id = 0) : m_id(0) {}
    
    int getId() const { return m_id; }
  };
  
  class Derived: public Base
  {
  public:
    double m_cost;
    
    Derived(double cost = 0.0, int id = 0) : Base(id), m_cost(cost) {}
    
    double getCost() const { return m_cost };
  };
  
  int main()
  {
    Derived derived(1.3, 5);
    cout << "ID: " << derived.getId() << '\n';
    cout << "Cost: << derived.getCost() << '\n';
    
    return 0;
  }
**/

/**
  This is the JS from C++. Is this correct way to convert?
**/
const _id = Symbol('id');
const _cost = Symbol('cost');

class Base {
  constructor(id = 0) {
    this[_id] = id;
  }
  
  get id() {
    return this[_id];
  }
};

class Derived extends Base {
  constructor(cost = 0.0, id = 0) {
    super(id);
    this[_cost]= cost;
  }
  
  get cost() {
    return this[_cost];
  }
};

const derived = new Derived(1.3, 5);
console.log(`ID: ${derived.id}`);
console.log(`Cost: ${derived.cost}`);
console.log(Reflect.ownKeys(derived));