Using another class variable in Javascript

Question

I have the following class;

class Banco {

constructor (agencia, conta, saldo) {
    
    this.agencia = agencia
    this.conta = conta
    this.saldo = saldo


exibir () {

    console.log(this.saldo)

 }

}

Let’s say I want to use the agency variable in another class

class novoBanco extends Banco {

    exibir_agencia () {

        console.log(this.agencia)
        
    }

}

In this above scenario, I still need to pass the variable as a parameter of the new class:

var exemplo0 = new Banco('1111-1', '22222-2', 0)
var exemplo = new novoBanco('1111-1')
exemplo.exibirAgencia()

Is there any way to use this variable in another class without having to pass it as parameter of the new class?

Answer 1

There is the conceptual error, or the question does not make sense. It has another class, but has no other object. It would be good to read What is the difference between a class and an object? to better understand.

Inheritance is a way of creating a new class, that is, a model, without having to specify everything that already exists in the mother class and serves well for the daughter class. It has nothing to do with harnessing data in the object, and in fact it doesn’t even make much sense. Maybe I didn’t quite understand how inheritance works, because I would use it, even if it hardly makes sense of truth, I’ll consider it just to test the mechanism.

When you are creating an object and storing in exemplo is only dealing with the daughter class. further, there is no variable passing anywhere.

Strictly should not only pass the agency. In fact a coreto code should test this and not accept if the other data is missing.

There seem to be other conceptual errors but I won’t talk because I have no more information.

The most organized code (pay attention to the details)):

class Banco {
    constructor(agencia, conta, saldo) {
        this.agencia = agencia;
        this.conta = conta;
        this.saldo = saldo;
    }
    exibir() {
        console.log(this.saldo);
    }
}

class NovoBanco extends Banco {
    exibirAgencia() {
        console.log(this.agencia);
    }
}

var exemplo = new NovoBanco('1111-1');
exemplo.exibirAgencia();

I put in the Github for future reference.

Answer 2

You can use the concept of getters and setters to persist the data. in a very basic way follows an example below using static class. but this is not the best way to do it, but only to show that it is possible, and realize that the Bank Class is no longer extended.

For if you extend Banco in NovoBanco the variable agencia will be reset and returns undefined because when extending Bank, the builder will renew the past values, if nothing is informed the return will be Undefined.

static class Foo { 
  public static agencia;

  static setAgencia(a) {
    self.agencia = a;
  }
 
  static getAgencia() {
    return self.agencia;
  }
}


class Banco {
   public data;
   
   constructor(agencia, conta, saldo ) {
        this.agencia = agencia;
        this.conta = conta;
        this.saldo = saldo; 
        this.data = Foo.setAgencia(this.agencia);
   }

   exibir() {
       console.log(this.saldo,Foo.getAgencia());
   }
}

class NovoBanco  {
  exibirAgencia() {
       console.log('Exibindo agencia\nGravada em new Banco():\n Angecia: ',Foo.getAgencia());
  }
}

var getConta = new Banco('1234-5', '22345', 0)
var exemplo = new NovoBanco();
exemplo.exibirAgencia();

But pay attention to the concepts of OOP. as @Mineiro explained.